If you were his caretaker, I think it would be likely that you'd want to discourage alcohol use or sexual involvement until he re-learned things, though.

The caretaker's POV is very important to this, and I agree with your opinion. Perhaps a more appropriate comparison than an infant would be to someone who grew up in a bubble of sorts, lacking the "normal" experiences. While I expect someone like that to be very messed up, he'll still qualify as an adult.