A pertinent comment from Wikipedia about trolls.

http://en.wikipedia.org/wiki/Internet_troll


Trolls...make argumentative posts in an attempt to discredit another
person,
concentrating almost exclusively on facts irrelevant to the point of
the conversation, with the intent of provoking a reaction from
others.


The key element under attack by a troll is the forum or group's
recognized and agreed upon power structure.