Dave Weigel lays it out:

One of the more jarring passages in Rick Perlstein’s “Nixonland” is his recounting of a popular myth that went around Iowa in 1966, the year of the conservative backlash against the Great Society. The myth was that black gang members on motorcycles were going to head from Chicago to ransack Des Moines. Reading this in 2008, it sounded preposterous, the kind of thing that no one could believe in the country that was about to elect Barack Obama. But [Fox’s Megyn] Kelly, under the guise of journalism, is working to create a rumor like this in 2010. Watch her broadcasts and you become convinced that the New Black Panthers are a powerful group that hate white people and operate under the protection of Eric Holder’s DOJ. That “Megyn Kelly DESTROYS Kirsten Powers” video that I mentioned begins with her introducing a clip of a town hall meeting with Rep. Brad Sherman (D-Ca.) in which he gets an angry question about whether the DOJ has a policy of not prosecuting African-Americans.

“I am extremely sure that we do not have a policy at the Department of Justice of never prosecuting a black defendent.”

The crowd rises up. “Yes you do!” shouts one voter. When Sherman says he doesn’t know much about the Panther case, the crowd erupts in boos. They’ve been driven to fear and distrust of their DOJ by round-the-clock videos of one racist idiot brandishing a nightstick for a couple hours in 2008.

The facts do not matter. This is precisely why people like Mr. Frazee are critically under-informed; it’s not so much that they don’t pay attention, it’s that if they are paying attention, it’s most likely they are watching FOXnews. Furthermore, anyone that grew up in the age of Cronkite has an implicit trust of television news: they simply must be making at least some effort to give us factual information…sure, it’s hyped here and there, but it must be all basically true. That’s just how it works.

And, in classic Dunning-Kruger fashion, they have no way of testing that hypothesis, are assured of their facts, and contrary, accurate information will only cause them dismay and harden their attachment to the preexisting falsity.