I kind of get what you're saying about his reaction, because I can see my H responding the same way. He would probably feel threatened for the same reasons.
BUT, I don't get how your attending a meeting in a different room, albeit same time, same location, would somehow compromise HIS ability to do his thing in AA, unless you were holding a glass up to the wall so that you could hear what he was saying.
If you want to check out that group, I say go for it.