Megan has an excellent post on why partisans of both sides are so willing to believe idiotic things about the opposition (such as Hillary Clinton being one of the 20 worst figures in US history, for example). Her short explanation is that most people wall themselves off from alternative viewpoints.
This example echoes my own experiences, even with the most intelligent of Democrats:
An example: the 2000 presidential race. The entire City of New York seems to have collectively forgotten that the newspaper recount occurred. I mean, I spent quite a lot of time hearing about how when that recount came out, it was going to expose the Supreme Court as a partisan sham, and George Bush as the undeserving usurper who stole the election. Then the People would rise up as one body and throw the Republicans out, never to return.
Then the newspapers published their results. And everyone who had been anticipatng the outcome with only slightly less enthusiasm than a Trek convention waiting for William Shatner to come onstage — all those people didn’t just stop talking about it, but seemingly wiped the results from their mind. It is even now common at gatherings of New Yorkers to hear bitter recriminations about the Supreme Court stealing the election for Bush, even though the recount seems to have shown, as conclusively as anything can, that Bush would have won even if the Supreme Court had mandated the exact recount Gore’s team wanted. It isn’t disingenuous; they do not know this fact. And how do they not know it? Because there are five million or so other people around who constantly tell each other that the Supreme Court stole the election for Bush. And like anything that one hears over and over from sympathetic sources, it becomes true to them, just as most of us love our siblings even though we’ve never really stopped to consider the matter. Everyone says that people love their siblings; therefore it is so.
But this is not limited only to Democrats:
Not, mind you, that I think Republicans are more aware of Democratic arguments because they are naturally more intellectually curious. They are more exposed to alternative viewpoints only because they haven’t got a choice. Most of their newspapers, weekly magazines, network news, etc. run liberal (even the ones with conservative editorial pages, as you’ll find if you ever talk to Wall Street Journal reporters).
As a libertarian, I’m actually worried by the rise of Fox. It’s nice to have an alternative viewpoint out there, no matter how pugnacious. But Fox represents an opportunity for conservatives to wall themselves off in their own intellectual ghetto so they won’t ever have to ask themselves uncomfortable questions, or go through the coolie labor of reworking one of their political ideas.
Such insularity is awfully dangerous.