This entry by "somian" from the use.perl.org feed is a fascinating read. It analyses his experiences on #perl on Freenode. I've never been there, although I did pop in on #gentoo, when I had a vexing question for which RTFM wasn't possible because I didn't know which FM T R. Anyway, somian's thoughts apply to many other online chats and forums, and I'm not familiar with his specific situation.
On one hand, I see what he means. I've felt similar disappointment with the "groupthink" I've found - especially annoyance at the assumption that my nerd mojo somehow implies that I hold a whole set of opinions or behave a particular way.
But the tendency of people in a group to mercilessly attack outsiders is a deep, human-naturey thing (see my post on mockery). Part of the reason people form into groups at all is out of a common thread between them. Frankly, they didn't form the group to talk (in a non-dismissive way) about people who are different than them - they formed the group to talk about their interests.
Practical upshot: nerds aren't immune from mob mentality, regardless of whether they happen to be "right" about something or not.