^ Because, if you know i is prejudice, you know you're going to be excluding a lot of people from healthy social interactions unfairly, right? You're going to offend them, because they identify themselves with those cultures, races or whatever you're prejudicial against. Edit: Rational doesn't mean right or wrong, and you're calling rational something that explains why you think like this, which is a "justification" of sorts, but it doesn't give you extra rights or anything. People put a lot of effort and thinking even for "dumb" things. Take nazis, kkk or other hate groups. Still, they're wrong and whatever experiences they had don't matter.