Snickersnack: True internet trolls feed off their target's distress and rage. It's a form of sadism. I fell for them for an embarrassing number of years because I couldn't accept that such people actually exist. Fortunately they're not very many of them.
BadDecissions: ... you make them sound like some kind of terrifying demon, instead of--which I suspect to be closer to the truth--bored teenagers looking for a laugh.
I would never do that. A skillful troll is far worse than any demon. ;) Such a beast can hasten the death of an online community. IMHO, they're a bigger problem than spam and lazy newbies (who can seriously lower the signal to noise ratio).
Don't let age fool you. Bored teenagers have been known to torture small animals for fun. Adults too for that matter.
BadDecissions: edit: Is anjohl doing a demonstration? You see the exact same "You called it a theory, therefore I win!" bullshit from creationists.
Only your opinion matters. If you think someone is trolling you the usefulness of continuing the discussion is zero. It's a Godwin-like moment. Whether they are actually a troll or not is irrelevant.