how can they be stopped?
I guess you need an 'official club' with one rule.
Rule 1: No other rules and no frequency board.
Personally I don't understand the harm in having a frequency board. Especially if a more and more people decide to come out and fly...it might get difficult to memorize 20, 30....60 peoples frequencies.
Without a club or any rules doesn't that simply leave it to everyone to make their own rules? It's public land so you can't kick the guy out ...
Mike