Why did John Milton bother the guy in the subway train?

Question

When John and Kevin are riding the subway train John intentionally "gets the attention" of a very hostile commuter. In the shot prior to John pulling the face at him it is clear that the commuter is not paying attention to him at all, hence my assumption that John is the one starting the conflict. He then goes on to influence the commuter to commit a crime(s).

Is this a simple case of John influencing others around him to sin just for fun or is there more to it? What exactly is the meaning behind this scene other than showing John's power to influence/manipulate? He talks about delegating just before the conversation starts, so is any part of his conversation with Kevin prior relevant here?

Answer 1

John tells Kevin that he doesn't like to micromanage. He "finds the talent", and then he "delegates". What he's saying is that he finds people who could easily commit a horrible sin, and then he guides them on the path to sinning.

While John is telling Kevin this, he's staring right at the man with the box-cutter. The reason is that he sees his next "person of talent" (someone who can be led to sin). He then easily influences the man to go commit murder or double murder. During the conversation, John demonstrates that he is "all-knowing", since he knows about Carlos, he knows what Carlos and this man's wife are doing at the moment, what they're going to do soon, and he even knows what color bedspread they have. (It's green.)

After the two men leave the train, Kevin is impressed that John accomplished that. John spins a lie that feeds into Kevin's ego: "I told him that if he didn't leave us alone, you were gonna kick his ass." Kevin just laughs, taking the compliment. Kevin's sin of vanity is a theme throughout the movie, right up to the climax of the movie when John names it explicitly.