Just to clarify a legal point here: I'm not a lawyer, but my understanding of Freedom of Speech is that it does not apply to people who are on private property. In this or any other internet forum, you are effectively a guest on another person's private property. That is why a moderator can legally and constitutionally delete your comments or ban you from the forum.
This is the point that needs to be clear. Our Freedom of Speech is guaranteed to prevent the Government from prosecuting anyone with dissenting views. However, it needs to be remembered that our freedom of speech does not give us license to violate other people's freedoms.
For example, I have Constitutionally guaranteed freedom to disagree with a local church. My Freedom of Speech means that I cannot be prosecuted if I express those disagreements in a public forum. However, Freedom of Speech does not mean I can barge in on their services and interrupt them with a loud monologue on everything I think is wrong with their doctrines. Their right to peaceful assembly and to believe as they see fit is also guaranteed by the Constitution, and they would be well within their rights to ask me to be quiet, or to leave, and if I refused, to have me arrested for trespassing and creating a disturbance. The church is
their property, and on
their property, they have the right to not be subjected to my diatribe.
These forums belong to the owner, who establishes the rules of conduct for participation herein. Some such forums or groups are very strict regarding no off-topic discussions, regardless of how much interest there might be in the topic. Participants in such a forum should know the rules, and if they're bothered by adhering to them, should seek another forum more to their liking. Otherwise, they should not be surprised or offended when the rules are enforced.
I used to be the Admin on a player-run server for a MMORP game, and we often ran into this same argument. The owner of the server had rules, which included keeping the game "family friendly" by not allowing profanity or sexually explicit discussions. Players who signed up to play on this server (for free, mind you) had to agree to these rules, and still, some would cry that I was violating their "free speech" rights when I took them to task for inappropriate dialogue.
Free Speech was never intended to give us carte blanche permission to say whatever we want, wherever we want, and whenever we want. You can always test this if you like by yelling "BOMB!" in an airport, and then telling all the security people that it's your right to do so because the Constitution guarantees you Freedom of Speech, regardless of possible repercussions.