James almost sounds like Ron when he jumps to stupid conclusions like that. It irks Harry, but, well, he loves his son to death. Even when he's being ridiculously immature.

Reaching out, Harry hooks his grip into James's soggy collar and yanks him back.

"Oi. I expect you to show him the same courtesy you'd show anyone who's a friend of Al's or Lily's." Harry knew he'd done the lecture enough times, but it really just didn't seem to sink in with this one. "If he does something you don't like, walk away. Come to me or Mum. But don't push things." As he knows James has a tendency to do.