Every forum should have a restricted area for those members who just want to have an argument. If their behavior suggests that's all they want, their account access should be restricted to only that area for a prescribed period of time. I think that is the best way to handle people that don't want to be civil or stick to the subject at hand - sort of a modern day version of this:
https://www.youtube.com/watch?v=kQFKtI6gn9Y
https://www.youtube.com/watch?v=kQFKtI6gn9Y

