I haven't been over to the Rangers/Flyers thread in question, so I can't speak for that. But I have been a message board moderator and site co-administrator on several sites for close to six years, so I can speak with a little experience there.
All of those boards and sites I worked with were literary, movie, and just general message boards. My fellow moderators and administrators and I deleted comments all the time. Depending on the size of the board and the membership, there could even be multiple deletions of posts in one day. It wasn't arbitrary, though; if the sites' rules were being broken, the individual post in question was either edited or outright deleted. We would leave a note in the thread as to why. [comment deleted for flame-baiting--tancred] That way, the poster would know who edited it and why. The other members would also know, and that would give them an example of what they could or could not do. The moderator would then email the violating poster, explain everything, and warn them. Usually, a person who was warned three times was suspended. Anything after that, and they were banned. If a violation was really flagrant, they'd be banned outright. This was especially the case if posters attacked one another verbally. One snide remark or instance of name-calling just breeds more. It can't be tolerated.
Simply put, free speech doesn't exist on message boards, because each board is "owned" by a private individual. That owner can set any rules they wish (as long as they are not illegal–things that would basically amount to fraud, prostitution, etc), and anyone joining that board must abide by those rules. Its usually part of the membership agreement each of us agrees to when we sign up.
The most perfect explanation I've seen of this is from a board I used to moderate at. Here is a link to their posting policy. It was a shining example of what a message board should be, and made everything run like clock-work.
The idea of having free speech on a private message board just isn't plausible or real.
From all the years of experience I had moderating and administering other message boards, I'm quite surprised rules against flaming, name-calling, and other verbal attacks aren't enforced as strictly here at HTR. I don't mean this as a criticism; I'm a fellow moderator, so I know the job is a lot tougher and more time-consuming than it seems like it would be. Its just that the attacking and abusive posts are so common-place here, and they would never be allowed at any of the other sites I've worked for.