Responses
Lay the blame where it's due: he was a manipulative ass right from the moment he first met and decided to "date" the old man for his money... He just didn't know the old man would turn out to be another manipulator himself.
TBH, Monkey see Monkey do.
The guy's probably a manipulative ass because he had a firsthand experience to seeing how far that gets you from the stepfather. I don't blame him, and it kind of makes his character more interesting.