Been so long since I saw the episode, I forgot this incident. But my lingering impression is that there were a couple of references in the first 2-3 seasons of things AJ did with animals as a child that suggested the kind of emotional detachment that would enable him to inflict suffering on others with no remorse and, in that way, make him a good candidate to follow a mob "career" path. I think technically there is a distinction between sociopathy, as it is defined in psychology, and the characteristics of many mob members. For one thing, sociopaths do not do well in groups of any kind and tend very much to be loners and nonconformists whereas mob culture is predicated upon grouping and conforming to a set of principles, as counter as those principles may be to mainstream, more evolved values and cultures. But certainly a subset of mob folks are as devoid of the capacity for compassion as are genuine sociopaths, and we saw a number of those on the Sopranos through the years.
Tony, his spirits crushed after b-lining to the fridge first thing in the morning: "Who ate the last piece of cake?"