Sticking a knife to someone will cause him die. People don’t want to die. So they come up with some arrangements. Let’s not kill each other. But people are selfish. So they said, okay, those who kill, we kill. Tada…. We got laws and justice. Then we don’t kill each other. That would be the scientific explanation of morality. Interests of the powerful.
Still… Religious answers maybe more correct than liberal. Religious people know that you need to kill to prevent murder. Liberal that understand evolution theory doesn’t.