I actually did quit a bit of research for this topic while doing a hub about if serial killers were made or born. All of the statistics show that they are more often made than born that way. While I have no sympathy for people who do bad things it is quite amazing to look at the brains of people who are psychopaths and really seem to think what they are doing is justifiable.
It also is quite logical for someone to be a psychopath when they have been born in to horrible lives. The lack of empathy can be easily explained by feeling like others never seem to have it as bad as they do or did. The anti social behavior is explained by always feeling different and being made to feel insecure as a child. Being violent can be explained by being taught violent behavior from a young age while their mom beats them or their dad gets drunk and beats mom and them.
While many of us who had horrible childhoods grew up and turned out quite normal some I believe just can't get past it. Being a psychopath is like having a protective net around them at all times that keeps them safe and in control.