This is a post I put up on a BBS somewhere in response to some people who were really insistant upon the moral good of God and Christianity. Now, I'm Roman Catholic by birth and how I was raised, but...
Well, this is a very philosophical discussion, ain't it?
Umm, your belief system is formed around the most basic instinct in humans - survival. (a good discussion about this is in Robert Heinlein's book 'Starship Troopers' - more philosophy than fighting, unlike the movie).
Now, as a child you learn how to survive, and part of that (for most kids) is listening to what your parents tell you to do so you avoid getting spanked and punished. Moral philosophy and beliefs are passed down from parents to children, as long as the parents take that lead role. Otherwise these beliefs come from peer groups or other caregivers.
Contrary to popular wishes that 'man is basically good', man basically will try to survive. It just so happens that our society tries to reward positive people as opposed to criminals. This is most likely because society has grown to understand what helps make it survive, which is an ordered way of life. If everyone robbed and killed, there wouldn't be anyone left to rob from and kill.
Christianity doesn't have a stranglehold on moral righteousness. And it is not the perfect model out there. Consider Tibetian Buddhists. Low crime, very moral (by whatever standards you classify morality). Hell, they don't even go to war against China or offer resistence when they became oppressed. They believe that everyone is part of one continuum (this is a very basic description and a bit off, but bear with me). What they do affects everything else, positive and negative. Other religions seem to lack this and focus on 'what will happen to me' if you do something wrong.
Looking at it, religions are very ego-centric, with everyone looking out only to better themselves. The only way you get people to help others is by saying that and individual will help themselves by helping others.
So back to where morals come from - personal 'morals' so to speak come from the instinct to survive, within the environment someone is in, the society they live in, and the people who have influence upon them. Then they develop under the 'survival' instinct.
Why do you think it's so hard to 'reform' gang members. Their point of view has been created under different rules. They are doing whats moral in their world to survive. Why would we expect them to understand our world, or even want to? We don't want to go into their world.