In a way pein is kind of like naruto and jiriya. all they really want is peace. The main difference is that pein wants to acheive it irresponsibly by destroying everything and making wars bigger, so in the end there is noone left to have wars. I think that naruto will be able to change pein and make him see things in the same way naruto and jiriya see things and realize that what he is doing is wrong, after all naruto has the ability to pretty much change anyone/become anyones friend. Yes i know jiriya was killed by pein but i think that if pein changes naruto will be able to forgive him. I think it would ruin the story line if naruto becomes obsessed with revenge like sasuke and pretty much tries to kill pein no matter what. It is not like something like this hasn't happened before, when the sand and gaara(who was a psycho at the time) were forgiven afterwards, and gaara became good.