Hume on Moral Responsibility

I spoke in earlier posts about Hume's compatibilism when it comes to the question of free will. Hume believes that it is possible for necessity and liberty to coexist, mainly, as I argued, because one is free to act according to one's own desires. I said that even if these desires are determined by previous states of the world as well as the laws according to which it works, liberty is not infringed upon. Here is another question: If even one's desires are determined (according to which one makes decisions and acts), can they be held morally responsible for their actions?

First of all, this enough is clear: man is not responsible for his existence. Man is a contingent being, that is, man is dependent upon external factors for his existence. I said in earlier posts that even if a person could not have acted otherwise, he may still be free, namely because he acted necessarily according to the components that make him who he is. But can we be resentful (or grateful) to someone even if they could not have done otherwise? This question is in contemporary philosophy referred to as the question of reactive attitudes. Hume has this to say:

"A man who is robbed of a considerable sum; does he find his vexation for the loss any wise diminished by these sublime reflections? Why then should his moral resentment against the crime be supposed incompatible with them? Or why should not the acknowledgment of a real distinction between vice and virtue be reconcilable to all speculative systems of philosophy, as well as that of a real distinction between personal beauty and deformity?"

So Hume has made a point. Just because the world may have not been able to be other than what it is doesn't mean we can't distinguish between what is desirable and undesirable in it. But Hume only half answers the question of reactive attitudes. The tough question is not whether or not we can justifiably resent the actions, but whether or not we can justifiably resent the person who acted in such and such a way. I agree that determinism should not give us reason to give up moral distinctions, but I am quite unsatisfied with Hume's answer in that he does not address the real difficulty. Should we punish an individual for an undesirable action or simply recognize that it was undesirable (and possible try to rehabilitate the person instead of punishing him or her)?