I suppose it's the depiction of a mythical being living under rocks and bearing ill will to all passersby that's made it such a popular term in Internet circles. In the context of a chat room or forum it's easier to hurl barbs at an opposing viewpoint with that image in mind.
We all have an opinion and the right to express it, usually.
But for all the declarations of a free and open Internet the reality is that democracy is not universally embraced. Chat rooms and forums have "moderators" whose job it is to keep the discourse civil. Of course it's usually a volunteer position manned by something less than a degreed psychologist. Personal biases, immaturity and abuse of power come into play and suddenly the free exchange of ideas becomes a study in censorship.
If you're on the wrong side of the discussion expect to earn the label of the under bridge set. The funny thing is that the childhood retort of "takes one to know one" comes into play here.
Unless you're the type whose only purpose in life is to be disruptive it's likely you've been unfairly branded. With chat rooms less a democracy and more a fascist state there's not much you can do but find a more like minded group.
Keep in mind that "troll" is just a word tossed about as freely as words like "friend" or "gay" which bear little resemblance to their original meanings. There was a time, for example, when calling someone "friend" meant more than a checkbox on Facebook and "gay" had nothing to do with your sexual orientation.
Words co-opted for more of a lyrical convenience than anything else.
Since most people throw "troll" at even the hint of a contrary opinion it's almost amusing when you realize that they're guilty of their own charge. If an Internet forum is ruled more by fascism than free speech then attacking anyone with an opposing viewpoint to the group is in fact being trolled. In effect, practicing what they preach or denounce depending on your point of view.
There are still those whose only purpose is to disrupt and they're closer to the original spirit of the word. Though, there's a host of other derogatory terms with less ambiguity that are a better fit for that crowd.
So it seems it really does "take one to know one" Use the term too freely and you're guilty of the charge you level.
Best to not use it at all.