Voltaire : I may not agree with what you say, but I will defend to the death your right to say it.
Let's say you go to lunch with 4 other guys.
You start a conversation by saying "The world is round." (This is like starting a thread in a forum.)
The first guy A says "Yes, the world is round, it has been proven."
B says "Hmm. I would want to go round the world one day, and see if it's really round." (He is diverting a little. The conversation/thread might spin into travelling.)
C says angrily "The world is not round, it's flat, how can you be sure it's round?" (There are plenty in this forum like that, but they are not banned or condemned. Sometimes they are told off or scolded, but that's about it. The pap may ban him though, which is what you are saying this forum does.)
D says "The world is flat." He goes to the toilet and when he comes back, he goes near your face and says "The world is flat." While you are talking about women, he says again "The world is flat." When you start discussing about movies, he hums "The world is flat." to the tune of a movie theme. While you are paying the bill, he tells the waiter "The world is flat."
The next time you go for lunch, you won't want D along. You may or may not ask C, but you won't ask D. D is the equivalent of a forum or cyberspace spammer. In real life, he would be considered a lunatic.