Guys: Would you ever rape and murder a girl?

[robvalue]

No. I always try never to intentionally hurt any living thing more than necessary.

Morality is a personal thing. If someone simply doesn't care about how others feel, then there is no argument that could make them care. All that is left is pragmatism: you'll go to jail if you get caught doing crime, and generally people will treat you less well if you keep pissing them off.

Most people have empathy, meaning that hurting someone else is kind of like hurting yourself. So generally, such a person simply doesn't want to hurt others. Some people do entirely lack empathy, often through no fault of their own.

"God" has nothing to do with morality. It either offers its opinion, which is still an opinion however well informed, or it enforces behaviour it finds agreeable through threats/rewards.