We learn that there are angels and devils. Yin and yang. Same and opposite.

People trust people whose behavior they believe is like their own. It may be smarter to trust people whose behavior you can predict, but that is risky. It's lower risk to find someone who acts like you. Early on this created tribes. Behaviors were subject to scrutiny and differences were ostracized.

If you have doubts consider what happened to organized crime during World War II. No matter what you thought of the mob, the Nazis were the greater enemy.

In New Orleans if you are black the most different you can get is white and vice versa.