Hi R.,
Wow, I really feel for you. I think you're right about not wanting to pull him out, especially when he's not the one causing the trouble. I would ask the director for some written procedures for dealing with it - both my kids are in different schools and both schools have that, so I don't think that that is an unreasonable request. Both of our schools have what they call a "zero tolerance" policy. After a certain number of incidents (i think it's about 3), they pull the offending child from the classroom as punishment. In our case, it has worked wonders. All in all, I think it is the director's job to ensure that every child enjoys and wants to come there... so just by telling them that and the links you've seen to the other child arriving, should help get them to realize. Perhaps it would also help if other of the parents also complained.
The other thing to consider too is what age he is - ie if under child development standards what he's doing may be age appropriate in some way, and they may be just trying to wait it out.
I hope it works out!
M.