People tend to want to believe things that are flattering to themselves.

If you believe that most of the people around you are ignorant, racist bigots, then you get to be special and enlightened just by virtue of not being a bigot. Slandering the masses is a great way to feel good about yourself.

If, on the other hand, most people are not particularly prejudiced, then not being a bigot doesn't make you special - it just makes you normal.