There is no one either good or bad, but circumstances make them so.
There was a discussion of the Cumbria shootings in The Independent by Julian Baggini, of interest to freelance taoists everywhere. For your convenience, here are a few key paragraphs:
As soon as the identity of the Cumbria killer became known, people immediately started to ask what kind of man Derrick Bird was. And there were always going to be only two possible answers. Almost every perpetrator of an atrocity is assigned the role of either a monster who was bound to do great evil eventually, or an ordinary person who inexplicably flipped.
We need to understand that situation, rather than character, usually matters more in how people behave, not so we can just let everyone off, but so that we can better understand why people do wrong and do more to prevent it. Most people are neither bad apples nor good eggs, but soft fruit that can easily turn from ripe to rotten.
Left and right have traditionally made opposite mistakes in this regard. Conservatives have placed far too little stress on the role of social circumstances in criminality, imagining that poverty and social exclusion are mere excuses for criminality, not causal factors in it. The left, on the other hand, has tended to overplay the social, imagining that people have no control over how they respond to circumstances, that all criminality is the inevitable result of iron laws of economic determinism.
What we are now understanding is that it is not either/or.
I rest my case. Everything is a balance of one thing and the other.