I am not sure about this Basil.I think bad behaviour can occur with BYO or not.
Having booze a bit more expensive and controlled selling maybe more appropriate on big days but not during regular meetings.
There has been some pretty feral behaviour at times with people fighting, going onto the track, throwing bottles on the track etc which will happen with or without BYO.
But it is society again bowing to the 2% minority of dickheads who can't control themselves so lets change it and arrest the morons who muck it for the rest of us.