Is Morality True or Is It Useful Because It's True?

The two areas that I love to press into are justice and love. What I want to do is help the person feel the implications of their worldview. If it's reductively explained by evolutionary factors, the only reason you feel those feelings that injustice is wrong is because it helped animals survive. We could have evolved completely differently such that our moral intuitions about what is just and unjust would be the opposite of what they are. Can you live with that? Not which isn't the same question as saying, therefore it can't be true.