I frequently think that online forums perceive nonconformist outsiders to be the enemy, when oftentimes their own hostility and overreaction is the real problem.
This can hold true for offline groups as well.
[WS:] Yes, but this is much more likely to occur in online forums, because such forums do not provide any means of non-verbal emotional communication. Non-verbal emotional communication is essential in reading the intentions of group members and "regulating" interaction among them.
However, I never said that there is a problem with online forums - they work, but they have limitations, just like any other tool or means of communication. The problem starts when they are used instead rather than in addition to face-to-face interaction - but that has more to do with the nature of our society than with the nature of the medium itself.