JamesonCourage
Adventurer
But here's another riddle. Are american soldiers who snipe armed mujahideens and make those preventive air strikes evil? If during the battle one mujahideen shoots another one and then you shoot him in turn - would anyone think you killed an ally? Are american "adventurers" evil in general, because they go to other countries and kill the not necessarily evil people there?
American soldiers are in NO way adventurers. That is a terrible comparison.
I'd agree with your analogy more if the were part of a nation currently at war with trolls, which is something I allowed for in my initial post in this thread. However, if there is no such open, organized conflict, then there is no allowance. The troll is by all appearances an ally, and even inserted itself in between the PCs and the oncoming danger, making itself a target, and exposing it's flank to the players (a general sign of trust).