Oh and I'm going to add this as a concrete suggestion:
Volunteer community moderators (if you can't afford paid staff to police the boards).
"What? How can that work? That's a dumb idea!!!" Some might say.
However, I am active on a large political forum board that used to get extremely nasty around primaries and elections. The forum owners have no way to pay for staff so their solution was to tap fair-minded and judicious forum community members to volunteer for set periods of time (usually 3 months).
These mods would respond to alerts when people were acting like jerks. It actually worked very well and cleaned the place up although there's always the temptation for people to "go negative".
It boiled down to this: If you wanted to be insulting and disruptive, you were banned from posting for a few days. If you made it a habit, you were gone.
Of course you have to link forum identities to an email address or game key # or something like that so people just don't make new accounts.
Bottom line: People won't police themselves because of the anonymity factor. If you can't see someone's eyes and how they feel, it's just too easy to let your worst side show. Then, once the pattern is set even very nice people will cop attitudes just so they don't get beat down. The ground rules have to be set and enforced by Stardock.