If there is one thing I wish atheist/agnostic debaters would learn it's this: the moral argument for God is not an argument saying one must be a Christian in order to be a moral person. A few weeks ago I watched the Bill Craig and Chris Hitchens debate. Craig goes over the moral argument and then in Hitchens' rebuttal, Hitchens goes on in some detail how he is not a Christian yet he is moral and how he wants someone to give him an example of something moral he can't do as an atheist. Why does ask that? Of course he can be an atheist and be a moral person. Craig's moral argument does not declare the moral superiority of Christians or people of other religions.
Earlier in the week I was listening to the 2010 D'Souza and Ehrman debate. What does Bart Ehrman do? He goes into how atheists and agnostics are just as moral as Christians. Again, o.k.? Does that mean God doesn't exist? Not at all. That doesn't even mean Jehovah God doesn't exist. Giving stats on how some non-religious folks are just as moral as some religious folks doesn't undermine the moral argument for the existence of God, but it does show the objectivity of moral values and duties and we all know if objective moral values and duties exist, then God exists.
The argument is about grounding morality in God, not grounding morality in Christians, which would be absurd. If I can understand the focus of the argument, surely you Hitchens and you Ehrman can understand it. Give up on the statement "atheists are just as moral as Christians" and the challenge for Hitchens; both prove nothing.