I think you should identify with your character, but plenty of people like themselves and hate themselves. You just have to find out what's truthful for the person you're playing. When people talk about that, I think what they're saying is that as an actor, as Peter, you don't want to make a judgment that comes from your worldview about the character. Your judgments should be coming from the place of the character, and within that space, sure, you could love or hate yourself or whatever you think is most appropriate.