To add to isaac's post.
You could do what UBB and I and several others do.
Create a forum with access to only admins and trusted mods.
use as a temp delete forum repository.
So say you would ban him and then move all the posts to that forum
I use it for deleting posts in case I get over zealous and make a mistake, then I can just move it back.
Then once in a while I purge old posts from it.