[ Of course you'd say that, Naruto, but you don't really understand. Kakashi sighs. Maybe this was a bad idea, talking to Naruto about this. ]

You have to understand, Naruto... War is something that can send people into dark and terrible places. It can break people. Change them. Obito grew up in a time of war. And I suppose he put all of his faith into his love for Rin. So when she died... all the hope he had, everything he believed in, must have died with her.

What he's doing now... is an act of desperation. He does it, because he's lost all hope in this world, and thinks there's nothing here left to live for or believe in, so he wants to make a new reality. It certainly isn't a good thing, or the best thing for anyone at all, but Obito believes it's the best thing for us all, and in his mind, he's saving the world from itself because all he can see is hopelessness.