"...the world is full of people who go around believing they've got you or your neighbor figured out, there really is no bottom to what is not known. The truth about us is endless. As are the lies."
Philip Roth from The Human Stain
This is the source of racism as well as countless other types of human folly. Everything people think they know about other people. People love to feel wise and smart, and in control of the facts, except nobody really is, so that kind of knowledge really is just another form of BS.