IMHO, this is the problem. You guys ban somebody that you decided was more a negative force on the board than a positive one and then you set yourselves up to listen to all the banned person's buddies whine and complain about it. Then you get the first amendment activists, the rec.scuba free speech morons, and the democracy cretins in the thread and it all goes to hell in a handbasket. It was the same thing with the singles forum and look what an abomination that turned into.
Take a page from Machiavelli and hit hard and don't make excuses. If you need to do "evil", do it quickly and return to all the useful stuff you guys have to do behind the scenes. When you guys decide to do something, it has to be swift, certain, and you have to stand behind it. Tell people "this is the way it is, the decision was made, deal with it or leave". When people start calling you guys into question (esp. in public) and whining to high hell about it, ban them too.