There’s a great post today on a statistics blog I read, entitled Some things are just really hard to believe: more on choosing your facts. You should read this for yourself, but from my preconceived anti-ideological worldview the truth of it is almost self-evident. Here’s an excerpt:
Of course, it makes sense that people with different judgment of the facts would have different views on policies: if you think carbon dioxide doesn’t cause substantial global warming, you’ll be on the opposite side of the global warming debate from someone who thinks it does. But often the causality runs the other way: instead of choosing a policy that matches the facts, people choose to believe the facts that back up their values-driven policies. The issue about Obama’s birth country is an extreme example: it’s clear that people did not first decide whether Obama was born in the U.S., and then decide whether to vote Republican or Democratic. They are choosing their fact based on their values, not the other way around. Perhaps it is helpful to think of people as having an inappropriate prior distribution that makes them more likely to believe things that are aligned with their desires.
Or, more seriously, 
