How can there be any moral absolutes without a God? I have heard this question from so many theists. A better question is: How can there be any moral absolutes with a God? If God is the ultimate arbiter of right and wrong then there can be no moral absolutes. If God says murder your own child (like with Abraham), then this becomes the right thing to do in that particular situation. If 'right' is simply whatever God wills, then whatever God wills is right. 'God is good' means only that God wills what he wills. If God is truly good (in any meaningful, non-tautological sense of that word) then he is good because he obeys a set of moral principles external to himself.
No ethical theory I'm aware of is totally absolute. Even so, theistic morality has to be the most arbitrary ethical system conceivable. Utilitarianism, Confucianism, virtue ethics, social contract theory, all contain more absolutes than theist morality.