Here's a suggestion I have too often not followed myself:

Remember in the kids auditorium in grade school
when all the kids would start to say "shhhhhh" all at
once......until it reached a crescendo of sorts?
Well, here's my vaguely-related suggestion:

When ever he posts some insult, personal dig or non-constructive troll,
just ignore him.
Shine it on. Take a deep breath and don't in any way respond.
Not only will it help the newsgroup, but being ignored will really ****
him off.
A response (of any kind) is exactly what the trolling jerk wants.
So dissapoint him.

..........whoever he is. Might even apply to me on occasion.