DragonLancer
Hero
Spatula said:"A good X is a dead X" doesn't really wash for exalted characters, though, unless perhaps X is something that is, by its very nature, evil (demons, devils, undead). Most mortal creatures, and especially humanoid-type creatures are not kill-on-sight evil, even in a standard D&D campaign (trolls are only "usually" evil, for example). In Eberron, this is even more true.
Maybe but I still wouldn't punish them for this. Exalted doesn't mean that we should fall back on the old Lawful Stupid arguments.

Perhaps the thing to do is stage a scene where the trolls are fighting off the undead. Give the players a moments pause to wonder whether this is just infighting, or whether they have potential allies here afterall.