I've wondered about the same thing. I think perhaps a big part of it has to do with choice. A criminal might have some kind of biological deficit, but, it's coupled with an intense disregard for the people around them.
I'd like to think my brother is adopted, but he looks so much like me! ;)
I also wonder about family dynamics. I think, as a family, we used to coddle my eldest brother ~ when he said things that were cruel or irrational, my mom urged us to pull our punches with him as if he were somehow more emotionally frail ~ which he probably is. Still, this may not have been the best way to handle his tantrums and meanness. After my mother passed away, my brother's behavior got so much worse ~ he pretty well went off the deep end.
Of course I still hold out hope of redemption for him.
