It's not sex John is after, per se, but a nice tight hole, and that Rodney has one is mostly what counts.

I got that feeling from it too, which is what I meant in my comment about John treating Rodney like a whore. I think that may have sounded overly harsh, but what I meant was that all John seemed to care about was getting laid, and the thoughts, feelings or even identity of the person he was with didn't really matter.