I know about the backstory, but I don't think it's actually relevant (and I'm not sure it was ever incorporated into the game itself). He's not this way because of who he used to be before Cazador, a past he mostly doesn't remember. He's this way because of 200 years of severe, near-constant abuse, and because of what that would do to anyone short of a saint. The fact that we can see any change in him at all in so short a time is pretty remarkable.
