For the last year or two, several of my friends and I have fashioned a mini-tradition out of emailing political articles to each other. As often as not, these email chains die on the vine, with nary a reply in sight. But the occasional subject will touch a nerve, prompting a barrage of reply emails with all the requisite jousts and parries.

The most recent addition to the series was sent by Ben* with the subject line, “Sometimes, I just hate politics…” The email linked to a YouTube video posted by the Wisconsin GOP in which Democratic politicians denouncing hateful rhetoric from the right were juxtaposed against footage of liberal protesters engaging in identical behavior. To Ben, the hypocrisy was nauseating: even the specter of a recent assassination attempt, far from halting the partisan bickering, instead served as a catalyst for more of it.

Unable to resist the bait — and I use the word “bait” loosely here, as that was not Ben’s intention — I responded, arguing that “equating Hosni Mubarak signs [used by public-sector employees in Wisconsin]…with, say, bringing guns en masse to town hall meetings is a bit of a dubious analogy.” I concluded with the estimate that “realistically, at least 75% of [the hyperbolic rhetoric] is coming from the (very far) right.”

My email, in turn, prompted responses from Jesse and Ryan. The former utilized the analogy of a couple in the throes of divorce counseling; “the therapist’s goal in this case,” Jesse wrote, “is to get each individual in the deadlock to move from saying ‘He/She is monstrous’ to ‘We are both monstrous.'” Ryan similarly noted that “in my eyes there is substantially no difference between the extremes of either party” and suggested that “the biggest problem is that both sides have learned successfully how to manipulate the emotions of their audience into a frenzy where seemingly intelligent, thinking people will say stupid things that they would never say (and likely do not believe) outside of a political rally.”

The email chain has since died an abrupt death, as email chains are wont to do. But the conversation has lived on in my head, particularly in relation to the question of when, if ever, it’s appropriate or even possible to make a distinction between the rhetorical timbres of opposing political parties without completely abdicating a position of neutrality.

Some might claim that this very pursuit of neutrality is the problem: by identifying one side as inherently more harmful to the national dialogue, the critic’s objectivity has already become moot. There is an air of truth to this. But to dismiss finger-pointing outright as nothing but partisan gamesmanship only raises a more disturbing question. If such moralizing remains outside the bounds of meaningful critique, what check exists to restrain the political fringes from seeping into the mainstream?

This question, in turn, is further complicated by lessons from history. What constituted the “fringe” in the 1950s regarding civil rights, for example, became politically mandatory just decades later. In other words, widespread adoption of initially unpopular ideas has its place.

But what is that place? The boundary lines are far from clear, and today’s heated national debate over the nature of public rhetoric reflects the inevitable perils of attempting to delineate them. Of course, this hasn’t stopped anyone from trying. In recent weeks, a parade of commentators on the left have lambasted conservatives such as Sarah Palin, Glenn Beck, and Rush Limbaugh for their incendiary statements. And an equally impassioned rejoinder has emerged from the right, decrying liberals’ condemnation as mere political posturing. As is often the case, both positions are partly right. I, for one, am unable to buy into the progressive contention that the Tucson shooting of Representative Gabrielle Giffords was a consequence of violent dialogue in the conservative bloc. If anything, as more information emerged as to the character of Jared Lee Loughner, the would-be assassin seemed curiously devoid of a coherent political ideology.

Indeed, even if some link (however tenuous) could be produced to connect Loughner’s actions (and those of other unhinged citizens) to the words of overly zealous conservatives, there would exist a subsequent dilemma as to whether this fact alone justifies some sort of censorship. (I use the term “censorship” loosely here. It is unlikely any broad legislation curtailing free speech would result from the Giffords shooting, but a variety of lesser, perhaps self-imposed, edicts could produce a similar effect.) Political speech has always been rife with exaggeratedly strident and often morbid rhetoric. Even Palin’s oft-quoted “don’t retreat, reload” mantra, when viewed within the context of historical political campaigns, is not entirely out of line with precedent. Simply Google “violent rhetoric from the left” to view an extensive listing of physical and verbal abuse hurled by progressives at conservatives for proof that no single group holds a monopoly on foaming at the mouth.

In general, then, it seems that to criticize one side or the other for the vehemence with which they express their political ideals is nothing if not self-serving. In other words, when a Republican is roundly criticized for his embrace of higher military spending, for example, such criticism (justifiably or otherwise) will inevitably reek of partisan point-making. Just as often, advocates on both sides of the aisle will throw out figures and polls purporting to demonstrate clear public support for their preferred policy and accuse the other side of playing games with the facts to woo the voting public.

How, then, are we to determine when one side has truly crossed a line? Locating such a tipping point faces a myriad of risks, as any overtly partisan conclusion will alienate roughly half the population and do nothing to cure the problem. And yet it is vital that a line be drawn, however arbitrarily, because failing to do so would remove all traces of a moral compass from our political dialogue. Obviously, certain tests must be disallowed from the start. For example, one cannot use a subjective policy debate — i.e. health care reform — as the baseline by which all deviating perspectives are measured. Although many might like to disagree, in reality such arguments have no absolute moral victor. As with nearly any political dispute, there are pros and cons to each side. Thus, in the overwhelming majority of cases, one’s (seemingly illogical) adherence to one or the other policy cannot in good conscience be regarded as “crossing a line” simply on account of the policy’s content.

There is, however, another way. Unlike the vagaries of immigration law or foreign policy, some beliefs can be independently verified or disproved. In such cases, we thus gain a reliable barometer for the extent of delusion among adherents of a specific ideology. The most prominent such delusion in American politics today is the birther movement. According to a February 15 poll by Public Policy Polling (PPP), 51% of likely Republican primary voters believe President Barack Obama was born outside the United States. Even more alarmingly, an additional 21% remain “unsure.” This leaves a paltry 28%, or just over a quarter, of likely GOP primary voters who believe the president legally holds office.

Now, a few caveats are in order. First, the sample size of Republican primary voters is small (400), and the margin of error is 4.9%. Furthermore, as this measures the views of the subset of Republicans who plan to vote in the 2012 primaries, the poll necessarily excludes many moderate Republicans who will sit out the primary election season. But even taking all this into account, the reality of a profoundly denialist portion of the electorate remains. (Even assuming the maximum margin of error, 46% is an astronomically high percentage of believers in an idea that has been systematically disproved.)

Similarly, last August a poll by the Pew Forum on Religion and Public Life found that 31% of Republicans believed Obama was a Muslim. (A TIME poll placed that number much higher, at 46%, but the sample size was smaller than Pew’s.) This is significant in that it encompasses all Republicans, not just those likely to vote in the primaries. Thus the Pew poll represents a much more holistic account of what is considered mainstream within the Republican Party. Whether the TIME or the Pew poll is taken more seriously, the result is basically the same: somewhere between a third and a half of Republicans (as of August 2010) erroneously believed Obama was a Muslim, once again despite seemingly incontrovertible evidence to the contrary.

Such widespread self-deception is not entirely without precedent. In September 2006, TIME published an article titled “Why the 9/11 Conspiracy Theories Won’t Go Away,” which cited a Scripps-Howard poll finding that “36% of Americans consider it ‘very likely’ or ‘somewhat likely’ that government officials either allowed the attacks to be carried out or carried out the attacks themselves.” (This poll stands in stark contrast to my claim, in the above-mentioned email chain with my friends, that the 9/11 truther movement never gained traction. Clearly, my memory is less reliable than I’d thought.)

Of course, that figure includes all Americans, not simply members of one political party (although various polls collectively portrayed liberals/Democrats as significantly more likely than conservatives/Republicans to believe this interpretation of events). It also refers to an event that is slightly less provable than, say, one’s place of birth (identifiable by birth certificate) or religious affiliation (verifiable via long-term church membership, the accounts of close acquaintances, etc.). And finally, by using language such as “government officials…allowed the attacks to be carried out,” the poll makes ample room for non-sinister cousins of the truther movement, such as a failure by American intelligence agencies to take threats seriously. This, of course, would significantly alter the implications of these claims.

But an inescapable conclusion lingers, which is that — when presented with a catalyst for latching onto questionable or outright false ideas — vast numbers of both the right and the left are susceptible (perhaps to varying degrees, but susceptible nonetheless). As of several years ago, a sizable minority of the American population felt skeptical about the official version of the 9/11 attacks. And today, a Republican primary voter who believes Obama was born in the United States would find himself in the minority.

In fact, the story of the 9/11 truther movement may provide the solution to the contemporary birther epidemic. If the goal is to eradicate such falsities from the public square (through soft, not hard, power), the relative absence of 9/11 truthers from recent discourse provides an instructive example. As I see it, the single most effective response to the truthers was its eventual systematic neglect both in the mainstream press and among elected officials. Especially in comparison to today’s birthers, as time went on truthers enjoyed relatively little press (favorable or otherwise) and even less attention from public officials. Their movement, then, endured a relatively quiet death.

In contrast, birthers can thank both ends of the ideological spectrum for providing nonstop coverage of their efforts. From the right, they are encouraged by the likes of FOX News; from the left, they are excoriated by MSNBC. Furthermore, the explosion of the blogosphere and social media has helped to spread the message for birthers in a way that truthers could never have achieved just a few short years ago.

Both sides are to blame. House Speaker John Boehner, in an interview on Meet the Press with David Gregory, sidestepped responsibility for the growing clamor of birthers within his ranks, stating that “it’s not my job to tell the American people what to think” and dismissing one representative’s birther-friendly remarks as a joke. Other members of the Republican Party have shown similar reticence in regards to confronting the far right. Countervailingly, one cannot escape the suspicion that the birther movement is itself partially sustained by the left, which is only too happy to use them as a foil in the endless jockeying for public approval.

Today, the pendulum of inanity has swung to the right. In a few years, it may be the left. But regardless of cause or content, it would behoove those of us who haven’t fallen for baseless beliefs to spend less time focusing on those who have.

*Names have been changed.