I am inclined to think that you are right about simple. He is actually trying. He even thinks he is making points. However, there is no evidence at all that he is capable of actually discussing anything.
I don't like suspensions, so I am not going to go for that right now.
I would suggest that simple be confined to the free for all or one single thread. Any deviation would be subject to suspension.
The single thread should be very, very simple. It should be a chance for him/her to demonstrate that s/he can actually carry on a rational conversation. If that fails then restriction to the free for all before any actual suspension.