Not this kind of troll.
Often we think of "cyber bullying" as merely a continuation of the in-person bullying someone faces in the so called real world. But, unfortunately, cyber-bullying can also be random, arbitrary, and unexplainable. Sometimes, someone has just decided, for reasons you cannot understand, to say truly obnoxious things, things so heinous that just thinking about them makes your blood boil, insults that DEMAND a response. And if you do respond, well, you've been trolled.