June 21, 2017:

OCD is only one component. He lashes out so hurtfully because he's lonely. He feels unloved, which firstly makes him angry, secondly leads him to feel there are no consequences. So what if he hurts people? They're nothing to him. Besides, they probably deserve it.

Carol and Simon teach him by example that compassion creates companionship.

Yet we should emphasize that it's his very selfishness which leads to transformation. He's a better man because he paid Carol's medical bills because Carol is the only waitress patient enough to serve him breakfast. It's because of his OCD and his loneliness that he needs for her to be at work. It's not altruism but his need which leads to change.