Ken,
You did the right thing because its one thing to say something that you can't substantiate once in a blue moon, but JJ did it almost daily. Opinion is fine, but to constantly take shots at people and books with no backing whatsoever is truly too much. He could say hey, I worry that such and such book is in trouble, but to just come out and take shots at their credibility crosses the line.
Only thing you can do is actually take his advice, give him his own forum, but ban him from all others. If people want to read him and be somewhat entertained by that, you could keep it aside where people know there is a major disclaimer. He said he wanted his own forum, well there is a way to accomodate him and allow most of us to keep our sanity.