Biggest fiasco I ever witnessed was when I joined the Megatokyo forums. Half an hour in, I posted an opinion on some topic somewhere. Now, you know me: when I post an opinion, it's lengthy, and I like to think intelligent, and usually pretty well thought-out. It also happened to contradict the opinion expressed by the thread starter, and about the fifty or so members (most of them with post counts in the thousands) who had apparently just come to the thread to say "yhea me too." I was civil about it all - I just posted what I thought, played the devil's advocate a bit, and then went and looked at a different thread.
During the five minutes before I went back there, They had managed to post about fifteen variations along the lines of "STFU n00b!!1", although only one of them was actually that curt and condensed, and, come to think of it, polite...
So, my next comment was, basically: "What, just because I only have five posts means I'm not entitled to think? Since when does being new to the forum mean I can't say what I think? Besides, I've been round various forums for YEARS, probably since before most of you had even heard of cooties..." and so on.
Looking back, I wish that I'd just told them where to shove it, and quit the forum then and there. That conversation quickly got ugly. Those guys were asses.
I think I stopped reading Megatokyo shortly after that...