Apparently I only flunked my math test because my teacher was an ideologue:
Everybody knows that our political views can sometimes get in the way of thinking clearly. But perhaps we don't realize how bad the problem actually is. According to a new psychology paper, our political passions can even undermine our very basic reasoning skills. More specifically, the study finds that people who are otherwise very good at math may totally flunk a problem that they would otherwise probably be able to solve, simply because giving the right answer goes against their political beliefs.
The rest of the study is illuminating. Best way to avoid it, if you want to be accurate, always sit down and do the actual calculation.