"Yes, that would be a symptom of the psychological effects of isolation." He sounds dry as a psychology textbook, and it's intentional. Come on, Joker, you're not stupid. "You're a living, breathing human being, and humans are social beings. Even I, a person who is no longer alive, need someone to confide in and talk to. Refusing to allow myself that is... Well, I can take a guess to why you asked, and ultimately, my inability to trust was the reason. Nothing you did or could have done differently."

If you want to be absolved, Joker, this is your guy. He'll beat it into you if he has to, but it would make him feel bad. The person in front of him is beaten down enough already - the question is just whether he's hit rock bottom yet.