I had to write this after the near-flamefest here (the audism posts) and on The Deaf Sherlock last month. Over the years, I've been a moderator in chatrooms and message areas. Sometimes the work is fun. But then there's the occasional time when you'll have a member who is quite abusive and openly flouts the rules.
In some cases, moderators need the ability to clamp down in order to prevent an explosive subject from getting out of control. It's all too easy for this to happen and I have seen groups going from active to meltdown dead in short time due to certain subjects being brought up. In some cases, the operators are forced to start over.
It's not a freedom of speech issue. It's about following the rules. Most forum rules are common sense, usually treat each other well, no attacks, stay on topic, that kind of thing. One to remember is that the moderator has the final word on things, reserving the right to moderate, edit, or delete comments. If members complain about something, the moderator will take action on that. There will always be some who cause trouble, known as trolls. They have been known to start flame wars.
For more on understanding what needs to be done, read these sites;
How to effectively moderate forums
Internet Forum Moderation...for Dummies
Internet Forums on Wikipedia
One must have flexibility in being a moderator without looking like a dictator, silencing everything that you disagree with. Neither do you want to be known as having a heavy hand and/or being a control freak.