right-wing extremism is being systematically fed by the conservative media and political establishment.

Now, for the most part, the likes of Fox News and the R.N.C. haven’t directly incited violence, despite Bill O’Reilly’s declarations that “some” called Dr. Tiller “Tiller the Baby Killer,” that he had “blood on his hands,” and that he was a “guy operating a death mill.” But they have gone out of their way to provide a platform for conspiracy theories and apocalyptic rhetoric, just as they did the last time a Democrat held the White House.

And at this point, whatever dividing line there was between mainstream conservatism and the black-helicopter crowd seems to have been virtually erased.

Yes, the worst terrorist attack in our history was perpetrated by a foreign conspiracy. But the second worst, the Oklahoma City bombing, was perpetrated by an all-American lunatic. Politicians and media organizations wind up such people at their, and our, peril.