A Parable
Once there was a boy that thought what he believed was true, and this made him feel good. It wasn't long before he thought that since he felt good, he must be good. Years passed and he realized that since he was good, he perforce, must be right. This belief that he was right morphed into the belief that he was righteous. So, everyone that believed differently than he ... well, they must be wrong, and therefore evil.
This boy finally died of old age never having taken one step beyond the gate of the kindergarten.