Flamer (flam ur)
1. One who insults people for the sake of insulting
2. An extremely flamboyant homosexual man.
Flamers have often been incorrectly called trolls. This confusion is understandable as one way of trolling is through flaming. However, a flamer only crosses over the troll boundary if they use other methods of antagonization aside from just flaming. In other words, a flamer's goal is to make a good insult, while a troll's goal is to piss someone off.
Essentially, a flamer is more about the flamer than the victim, the troll is more about the victim than it is the troll.
Flamer could have been derived from the common phrase, "Burned." Therefore, an attempt to "burn" someone could be considered a flame.
Flamer, when to describe a homosexual, could have been derived from the word "flamboyant".