I had to help moderate a large company Intranet forum for franchisees.
Some threw around insults about the company all the time and made all kinds of remarks. It heated up much worse with any company changes or software changes they did not like. Some things the company had to reverse course on because of it.
Thing is, it is a fine balancing act.
You come down hard all the time and you are a forum nazi and no one will post critical information at all. The community will fail and they may just go make an unauthorized forum somewhere else.
Companies need to see and hear the bad feedback as well as the good.
It really is a difficult balancing act, and most of the time the users can set each other straight. You should only get tough as a moderator on certain extreme things like foul mouths, spammers, flooders, etc.