» Sun Aug 12, 2012 8:25 am
The only reason to kill Parrthurnax is if you buy into the Blade's idea that the only good dragon is a dead one. Paar *did* do unspeakable things when Alduin was in charge, but he's also the one to help humanity master the Thu'um, as well as guiding the Greybeards so that it would not be misused. Not to mention the whole 5,000-year-sitting-on-a-mountain-and-do-nothing thing. However, Paar is up front in saying that he, essentially, can't be trusted as dragons have an inborn need to rule. But the afore-mentioned 5,000 year wait pretty much shows that you could at least trust him as far as you could throw him.
Of note is that the Blades say that they won't aid you if you refuse to kill Paar... despite them being sworn to protect and serve the dragonborn. The Greybeards won't help you out if you kill Paar... but they have a very damn good reason not to.
The scales, as presented in-game, are heavily weighed in sparing of Paar. At least with the Civil War, you can effectively argue for supporting either Ulfric or the Empire. Here? The reasoning for killing Paar is on extremely shaky ground.