"People are a direct consequence of their environment and morals/ values they are installed with from a young age."
People are not a direct consequence of their environment. I agree that part of a person is dependent upon his environment and upbringings, but not completely. I'm sure you would agree that genes control things like skin color, body size, hair color, facial features etc. You can't agure that genese do not control physical traits. Fat parents generally have fat children, and black parents generally have black children. Ofcourse this is not always the case, because gene inheritance is a complex process.
But why do you think its so unrealistic to believe that genes can also control behavior? Smart parents are more likely to have smart children, and aggresive violent parents are more likely to have aggressive children. Ofcourse, nothing is as simple as that, different combinations of many genes can create many outcomes, some of which are simply random chance generated.
And by the way, he did back up the gene explanation. He said that the MAOA (sp?) gene which codes for aggressive behavior was found in all the killers he looked at. Then he explained how the seritonum (sp?) floods and desensitizes the brain.