Theists: how do you account for psychopaths?

[Mr.wizard]

I think everything will make sense to us someday, and we will understand why.

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So the answer to this is not an easy one. And my reason is philosophical (though hopefully it's clear by now I don't use big, obtuse words when I philosophize). Still, your question is a tall order, and I have broken into three questions. Please choose which of the three is the sticking point for you (or if more than one is, choose more than one).

1) Is anything right or wrong at all? (metaethics- I think this is what you really want to know.).
2) Why is murder wrong? (this is what you asked, but without me filling in #1, the answer to this may be dissatisfying).
3) Even assuming that it can be demonstrated that murder is wrong, why should I not murder someone if I can easily get away with it? ("If God is dead, everything is permitted"-Dostoevsky).

If I didn't believe in God and thought morality was subjective, I still wouldn't murder anyone because of the whole empathy thing.

My question is #2, but since you said you have to answer 1 for it, go ahead lol.

 In order for people to reach objective conclusions their must be a shared goal, in the case of humans it's well being. Murder is objectively bad for the well being of humans, so we are able to say that it is immoral. Notice you asked about "murder" and not "killing", that's because killing could be moral or immoral depending on the situation.