Thanks for the replies!
Chroma, that's a good point about how making everyone a jerk wouldn't make Apocalypse World seem real. That passage you point to seems really relevant, too.
Sheryas, I don't agree with you that reason or humanity can be leverage. Maybe we have a different sense of what is meant by leverage, though. To me that word means something you control, so you can control another person by offering to use your leverage one way instead of another, like operating a lever. You want something, I can give it to you or not, so you do what I want so I'll give you what you want. In your example, I might tell someone what they are doing isn't smart, and that may be enough to convince you not to do it, but I don't have any leverage because what I do has no influence over whether or not your course of action is smart or not. I can point it out, but I don't have control over anything that might influence your actions.