This is a long excerpt, but I think worth reading (the article is by Diana Mutz in the 11/2007 issue of American Political Science Review):
Incivility alone does not dampen enthusiasm for political advocates nor the arguments they make. However, when uncivil discourse and close-up camera perspectives combine to produce the unique “in-your-face” perspective, then the high levels of arousal and attention come at the cost of lowering regard for the other side. The “in-your-face” intimacy of uncivil political discourse on television discourages the kind of mutual respect that might sustain perceptions of a legitimate opposition. Here the pattern of findings is quite consistent; close-up perspectives on uncivil discourse routinely damage perceptions of the candidates and issue arguments that subjects are already prone to dislike; that is, attitudes toward the least-liked candidate, and the perceived legitimacy of rationales for opposing issue positions.
When we lose respect for the experts/politicians on the other side of the argument, we are less likely to really listen to what they say. It becomes that much harder to change our minds in the face of counter evidence. It’s no wonder that our politicians can never agree on anything. Are they even listening to each other any more?