There is moral error and moral disagreement. If your values change because of moral disagreement between your past and future self, that is something you'd want to prevent. If, however, you are simply correcting your moral error, this should be encouraged. In this case, your future self is acting more moral than you are by your current belief system, since he understands it better.

I think most of my change in morality will be due to correcting moral error. As such, in a matter of dispute, I trust my future self over my present self.