Trolls:
An Internet “troll” is a person who delights in sowing discord in the forums. They try to start arguments and upset people. For whatever reason, they don’t fully understand that they are hurting real people. To them, other Internet users are nothing more than a kind of digital abstraction. Indeed, the greater the suffering they cause, the greater their ‘achievement’ (as they see it).
The anonymity of the net allows trolls to flourish. They are easily identified by the fact that they are constantly at odds with other members of the forum, and often “poke fun” at individuals they have disagreed with in the past, trying to provoke a reaction. They tend to beget more trolls and in fact group together and defend one another in order to make their behavior look legitimate.
Trolls create a paranoid environment, such that a casual criticism by a new arrival can elicit a ferocious and inappropriate backlash. When you try to reason with a troll, they win. When you insult a troll, they win. When you scream at a troll, they win. The only thing that trolls can’t handle is being ignored and reported.