Extreme BlackDiamond

and I would be happy to see the list owner come
down hard on the perp. Banishment?

You should make sure you know who the perp is before making such
pronouncements (or maybe it doesn't matter).

Not really. It's the list owner who should know who the perp is
before taking action.

In any case, it's quite easy to figure out who dragged the
dispute onto the list by checking the incoming messages.
In this case one person sent a private email and the perp
sent a profane reply copied to the list. Clearcut case.