Less Wrong has an excellent post on Creationism and Global Warming ‘Scepticism’:
We are, I think, dealing with that old problem of motivated cognition. As Gilovich says: “Conclusions a person does not want to believe are held to a higher standard than conclusions a person wants to believe. In the former case, the person asks if the evidence compels one to accept the conclusion, whereas in the latter case, the person asks instead if the evidence allows one to accept the conclusion.” People map the domain of belief onto the social domain of authority, with a qualitative difference between absolute and nonabsolute demands: If a teacher tells you certain things, and you have to believe them, and you have to recite them back on the test. But when a student makes a suggestion in class, you don’t have to go along with it - you’re free to agree or disagree (it seems) and no one will punish you.