Jake did prefer some people to others, depending on how much they pleased him. He was good at finding ways to control people psychologically, and enjoyed doing so. As an adult he became dangerously violent and he ended up in jail.
His parents felt like failures but it wasn't their fault. His personality disorder was the result of prenatal neurological damage they couldn't have prevented, and was no more something to feel guilty about than any other disability. His parents were loving people and did the best they could.
Personally, I feel sorry for anyone who is unable to love other human beings. While people with APD don't know what they're missing, that might be the worst disability of all.