"How are you supposed to burn down a forest and murder all the animals in there to catch the bandits who stole the king's gold?": and that's why we have druids. They did start out as monsters in the original Greyhawk supplement. They aren't good (at least classically) feel free to kill them if they get in the way.
See, I always do and then everyone's all "Why'd you kill them? They might have been helpful!" Liars!