I kind of agree with June, it's too much like washing the forum's dirty linen in public, and as onerous and time-consuming a task as it must be at times, I still think the only solution is for you to continue to referee the board as you see fit, Charlie.
You're a reasonable person - more reasonable than most of the rest of us, certainly - so why not just apply a simple rule: no ad hominem attacks (or to maintain the sporting metaphor, play the ball not the wo/man). Any posts that you feel breach that rule should be edited by the poster to take the personal stuff out, or failing that they will be removed completely by yourself. Anybody who posts here does so as your guest, and therefore must respect your decision as to where the line is drawn.
Naturally, some discretion might be expected, eg little digs between two long-serving world music magazine journalists/editors could be seen as less serious than anything that might happen between two complete strangers. The onus, therefore, will be on us posters to think carefully about the way we frame our responses to each other and to try to exercise some restraint if a thread or poster is winding us up.
(Zee, I'm not sure whether this type of board allows an Ignore Thread or Ignore Poster option? Might be worth switching that on, so that members can exercise it anonymously when they find their blood pressure rising. )