This goes back to my debate with Pejman. David Corn insists that the difference between right and left rhetorical extremism is that the right has "institutionalized their side's craziness." Juan Cole is blunt. George Packer concedes that George W. Bush was the subject of vile liberal rhetoric, but notes the unmissable scale of the difference:

Only one side has made the rhetoric of armed revolt against an oppressive tyranny the guiding spirit of its grassroots movement and its midterm campaign. Only one side routinely invokes the Second Amendment as a form of swagger and intimidation, not-so-coyly conflating rights with threats. Only one side’s activists bring guns to democratic political gatherings. Only one side has a popular national TV host who uses his platform to indoctrinate viewers in the conviction that the President is an alien, totalitarian menace to the country. Only one side fills the AM waves with rage and incendiary falsehoods. Only one side has an iconic leader, with a devoted grassroots following, who can’t stop using violent imagery and dividing her countrymen into us and them, real and fake. Any sentient American knows which side that is; to argue otherwise is disingenuous.

The right and the left both have intemperate voices. But here's the key: only the conservative movement counts the most vile blowhards as leading lights, embraced by the leadership. Rush Limbaugh, Sean Hannity, Mark Levin, Sarah Palin: these are among the most popular conservatives in America. Who are the folks on the left with equivalent popularity and influence?