Well I think your reaction is great. You let your Son say what he had to say and now you are letting it go. It isn't yours to own.
The only thing that's really disturbing is AH speaking "for" you. Including you in his correspondence without your approval is very disrespectful and I would, personally, follow up on that. Just because he doesn't like the way you do things doesn't mean he gets to speak for you.
That's huge boundary crossing. But hey, that's just me.