Rationality, Prima Facia Plausibility and Discussion

What makes rational discussion so difficult? Why, even when someone is clearly aware and intelligent, do people not believe her?

When I was watching the analysis of the Kerry/Bush debate, I was impressed at how little the debates actually mattered. That is, every intellectual and analyst said who won based on their opinion they had beforehand. Now, the debates weren't really intended to be a forum to change anyone's opinion. But, if you analyze a debate, you determine who won based on who had the better reasoning IN THE DEBATE, not who may or may not be "wrong" according to your parochial outlook.

That made me consider: What makes it hard to convince people that something's true? In debate, we learned to analyze warrants and reasoning for arguments and use that to adjudicate the round. Yet that is only appropriate for intellectual conversations. What are factors that impede us having discussions?

1) Emotions. This is an obvious barrier: When people get angry, or desperate, or shut up out of emotion, the conversation quickly ends. Yet I've seen discussions where people are remaining reasonably cordial, and yet little progress is made.

2) Skepticism. Were someone to come up to me and say, "The world is flat, here are hundreds of footnotes to prove it", I wouldn't believe them. It's not that I would have many arguments on hand to prove them wrong, surely not as much material as they did, but such a claim would be completely at odds with everything I had learned, and further I'd know that were I to research, I could easily disprove them. So, even when someone seems completely prepared and informed, people are likely to not believe claims that are totally at odds with their impression. Chomsky among others has talked about this problem. The solution here is, first of all, some humility and trust that the other person is not deluded or misinformed, and secondly, an attempt to reach out to common ground and give some history and background.

3) Value conflicts. Even if I believe someone else to be factually informed and my emotions aren't flaring up, I may simply disagree with their values. These are difficult to solve: If someone believes that killing people is fundamentally good, then I can't do much to bridge the gap between us. But if someone, say, believes that killing people is necessary because of overpopulation, then it may be possible to discuss better solutions and offer some background on the problem, as well as maybe convince someone that it's wrong to use other people as means to an end. The problem with value discussions, aside from the fact that people cannot be "wrong" or "right" about values, is that those values form an underpinning of discussion and are not often discussed openly.