New York Times columnist Ross Douthat plays the tired “the left and right are equally crazy” card:

Paranoia is a bipartisan temptation. Amid last August's town hall frenzy, there was a stir over a poll showing that roughly a third of Republicans believed that Barack Obama had been born outside the United States. Liberals trumpeted the finding as proof of the Republican base's slide into madness. But conservatives had a rebuttal: As recently as 2007, they pointed out, polls showed that a third of Democrats believed George W. Bush knew about 9/11 in advance.

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The Clinton-era conservatives who insisted that Vince Foster's suicide was really murder ceded the stage, in the Bush era, to left-wing cranks convinced that the British scientist David Kelly was bumped off by Iraq war hawks desperate to cover up their deception about weapons of mass destruction.

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And the ideological fringes are forever blurring into one another: Pat Buchanan can sound a lot like Gore Vidal, “truthers” and “birthers” often share common fixations, and both the far left and far right seem equally inclined to circle around, eventually, to pointing fingers at the Jews.

Vince Foster conspiracists enjoyed widespread acceptance and promotion by leaders of the conservative movement, including Republican members of congress -- and by the news media. That's why there were half a dozen investigations into Foster's death, despite the fact that each unambiguously concluded he had killed himself -- you had Republican congressional leaders playing amateur detective, shooting up pumpkin patches in order to “prove” that Foster was murdered. And the Birthers' lunacy was taken quite seriously last year by, among others, members of congress and a CNN host who promoted their theories on a regular basis.

The Truthers have never enjoyed that level of respect and influence among progressive leaders, or among the media. So while it's true that you can find liberals who believe far-fetched things, they don't enjoy nearly as much influence as their conservative counterparts. That's a good thing. It would be even better if the media consistently made clear that one side is much more prone to taking their fringiest element seriously.