Studies show that there is a large correlation between genetics and life outcome.

i.e. when treated badly, most people will end up bad, some won't. When treated well, most people will end up good, some won't.

There are people who are pre-disposed to do bad things, no matter what. There are people who are pre-disposed to do good things, no matter what.

See the stories about Romanian orphans for how a bad system can turn most people into functioning sociopaths:

http://www.livescience.com/21778-early-neglect-alters-kids-b...

Yet some still turn out OK.