I think that quality manners and ethics from admins and moderators brings forth quality conversation from your members. Act mature and you'll get mature. On my board I have no cersoring and no banning on any swear words, yet I rarely have any course language that rises above (or should I say "below") a "PG" rating.
If you allow immature, flame-happy, a-cussword-every-three-words hotheads to run your forums, you'll get more of the same from normal members.
And I agree that that racism should never be tolerated.
