First of all, I brought Bono up in passing; I wasn't comparing Cameron's recent efforts to what Bono has been doing for years.
Second, you're saying that even if Cameron does some good for the world, his ego negates it? Sorry, but that's ridiculous. If the guy can help prevent a significant chunk of the Amazon rainforest from being destroyed, I don't care if he has a YHWH-sized ego.
Third, there's a good chance the natives encouraged Cameron to don the face paint.