Technically, I brought up Christianity, and I did mention the forgiveness of sins (or at least implied it):

any morality he posses now would have to come externally, from the work of Jesus Christ.

However, now that I read my post I fear I may have not quite gotten to my point, which you state quite nicely in your post. From a Christian perspective, Bush is immoral because of his sin, as are all the rest of us. However, this is not what you were driving at when you first stated you believed Bush to be "moral". I think your intent (correct me if I'm wrong) was that you believe he displays virtues that outweighed his non-virtues, and is a man worthy of trust and being looked up to.

After that, things sort of devolved into talking about his use of drugs to prove that he's not moral. If we're going to adopt a "you must live a perfect life in order to be pure" attitude toward morals, then it's prudent to point out that this is exactly the claim that Christianity makes. Except that it also adds the idea that we've been provided with a foreign righteousness in the person of Jesus Christ if we trust Him for it.

This is the doctrine that Bush claims (as do I), and therefore to say that Bush is moral even though he has sinned is valid, if we believe in the imputed righteousness of Christ. However, not all (if many) here would agree with this doctrine. That leaves us with Peter's perspective that a user of drugs is not intrinsically immoral, except as far as breaking the law is considered immoral.

There is still the matter of this war and whether Bush's actions in it are moral. This is the topic being heavily debated, not only because we have different ideas of morality, but also because the are differing ideas as to what Bush's goals really are.