Republican thought police.
Much of this kind of behavior can be traced back to what Richard Hofstadter famously described as the "paranoid style" of the American Right. Conspiratorial conservatives have a tendency toward what Hofstadter called "the imitation of the enemy." Thus the Ku Klux Klan wore the vestments of the Catholics they despised, and the John Birch Society organized itself in secret cells and front groups modeled on the Communist foe. Contemporary conservatives believe that the most powerful institutions in American society are part of a liberal conspiracy. They feel this gives them license to create conservative counterinstitutions, from magazines to think tanks. But these conservative institutions--the Washington Times, the Heritage Foundation--are part of an ideological mission in a way that "liberal" ones--the Washington Post, the Brookings Institution--are not.
Exaggerated and crude claims of liberal bias have become an excuse for poor journalistic standards, and for shoddy intellectual ones as well. But the worst of it isn't the propaganda that passes for conservative thought these days. It's the deadly sense of enforced conformity, the stale air that blows in from the stagnant ponds of the Right.