Theists: how do you account for psychopaths?

[vulcanlogician]

Yes. If the natural world is just an accident without any sort of objective purpose or intention, there isn't much reason to think morality is grounded in anything greater. Which is why atheists typically don't think morality is objective, which makes sense.

Laws are an attempt to enforce basic morality in society. Some people might diagree saying: "We have laws against murder because otherwise society would plunge into chaos." This is only partly true. We need laws to maintain order, to be sure, but laws aim to do more than that. The law could permit parents to kill their own children if they so wished, so long as it was done before they reached the age of nine, and society could continue to function pretty well in these circumstances. But we don't allow parents to murder their children before a certain age. Why? As I said before, the law isn't just there to keep order--it is also a medium through which basic morality is enforced.

Let's say you go out for a drive in your RV, and you make a wrong turn somewhere. You find yourself in some strange land where murder is not against the law. It is some unstructured society consisting mostly of vagrants and vagabonds. There is no governmental body that enforces murder laws. But does this mean that murder isn't wrong? No! The fact that there is an enforcing agent is not what makes something right or wrong. Even if you find yourself in a strange land where there is no punishment for the crime of murder, this does not mean that murder becomes morally acceptable.

By analogy, even though we live in a natural world that is "just an accident without any sort of objective purpose or intention" that doesn't make murder right, even if it happens within the confines of such a world. The lack of a cosmic enforcer has no bearing on the moral dimension of our actions. Murder is wrong in a country with murder laws. Murder is wrong in a country without murder laws. Murder is wrong in a universe created by God. Murder is wrong in a Godless universe that seems to exist by pure accident.

There are two ways to look at Divine Law (assuming such a thing exists):

1. Murder is wrong just because God says so.
or
2. Murder is wrong independently of what God says, but he forbids it because he is loving and just.

Your assertion that morality can only be objective in a universe created purposefully by God, seems to indicate that you fall into the first camp. But I don't think you do. I think you accept #2. But as a thought experiment, let's follow conclusion #1 to its logical end. Let's say that God comes before you and tells you that (if you want to) you can murder your neighbor's wife. If you do this, you won't have to ask for forgiveness, there is no threat of eternal damnation--none of that. God has said that it is okay.

The question is: would you kill your neighbor's wife if God allowed it? If God allowed it, would that make it morally right? If the answer is no: why not? 

Maybe it's because killing this woman would deprive her husband of a wife, and her two children of a mother. Maybe it's because it is her life, and you don't have the right to take it from her. Maybe it's because she is a human being with dreams and aspirations, and your desire to kill her is superseded by her right to live. But if God gave you permission, would any of these reasons that murder is wrong change?

Morality can neither hinge solely on the utterances of God, nor is it in any way impacted by God's purposes in creating the universe. Otherwise, murdering someone would be somehow become morally right just because God allows it (even though, by any other metric, it is the exact same deed). And (assuming there is a God overseeing this universe) it would become morally right to commit murder in an exact carbon copy of this universe if said universe were to come about by happenstance.