No Way! There is no way in Oblivion I would kill Uncle Paarthurnax! (Heck, if it were possible, I wouldn't have killed Alduin if it was an option). My reason: His logic is sound. Not the bullcrap Blades logic of, "He helped us, therefore he needs to die." Yes, I get he did some horrible things to the nords/humans... but that was a thousand years ago. Seriously, get over it (Plus I'm a Dunmer, so I like to think their logic does not apply to me. In other words, I don't give a flying s**t). Second, Paarthurnax admits that he knows what he did was wrong, and that he maybe does deserve to die that is an instant win. You don't here the Blades admitting that their ancestors hunting an entire species to extinction was wrong. Plus, the Blades preach that the Dragonborn is supposed to be their leader (or at least that is how they make it seem to me...) and how it is their duty to protect you, then proceed to boss you around. Screw you too Delphine! Plus, the Greybeards and Paarthurnax were much more helpful than the other Old Farts. I can't even muster my evil Argonian assassin to kill him, and he eats other people just for the fun of it -_-!... Maybe later...
Lastly: Paarthurnax = Mario, that's an instant win