I believe there are different types of human brains, some have evolved for the good, some have evolved or not, to the side of not good. I look at it like a computer. It takes thousands of programs to run a "normal" computer. Take away a few of those programs and things just don't work correctly. Make sence?
Makes sense to me. I saw a study about psychopath. There are way more under us as we know. Some of them would kill other people, so we see them at some point. But the other ones who just are assholes and mock people, push them around and have no empathy are way more and often in positions like politics or high positions in companies. They are not full psychopath but enough that you would recognize it.