Ordinary people want to feel philosophically justified in hating evildoers and viewing them as the ultimate authors of their evil. This moral attitude has always been vulnerable to our learning more about the causes of human behavior—and in situations where the origins of a person’s actions become absolutely clear, our feelings about his responsibility begin to change. What is more, they should change. We should admit that a person is unlucky to inherit the genes and life experience that will doom him to psychopathy. That doesn’t mean we can’t lock him up, or kill him in self-defense, but hating him is not rational, given a complete understanding of how he came to be who he is. Natural, yes; rational, no.
Sam Harris, http://bit.ly/I5fquD