I think the movie did a good enough job with that. That scene where Eazy clearly had him dead to rights, the scenes with cube and Dre about him and the fact that they all said they'd get back together if he's not in the picture really illustrated that he was the one with the hand in the cookie jar and that Eazy wasn't as smart as he thought he was and that jerry wasn't as down as he thought he was. Just because he believed his own bull doesn't mean everyone else did or should and to me, the movie makes that justification very clear. Everyone is the hero in their own story so of course he'd believe he was doing the right thing.