As you continue to watch, you'll see Dexter has a VERY strong sense of compassion; he just has different ways of showing it. The only thing that really "makes" him appear that way is that his moral values obviously differ from most people's in that he'd rather kill a rapist/serial killer rather than give them the luxury of the justice system. Which makes total sense to me. While I DEFINITELY love the show... I question its validity as far as ASPD goes. Serial killer doesn't have to be synonymous to psychopath/antisocial. While he does have some traits, whether he actually has ASPD or is just severely otherwise traumatized mentally/emotionally is up for debate. : )