There's really no direct solution to the problem; you can't stop
forum trolls from coming to disturb the peace and order.
Unless we're talking about bringing the security of the forum to a
higher level; ip banning and etc. But then again, it's a lot of
work, monitoring and there is still no guarantee that the trolls
won't be back and all.
In an ideal scenario, the mod should be "well respected and well
loved" by the people; and the people disciplined and educated
enough not to feed the trolls.
Then again, in the real world... It's easy for the mod to lose
patience and be more autocratic than anything and it's also easier
for the people to be tempted by the trolls 
