In my opinion, his rationalization for entering the relationship would only have been valid if he had lived with the tribe, and adopted their entire culture. To take her to 20th century America, where he understood the culture, there, was breaking that culture's "rules". I understand that he assumed that she could adapt to modern life, but, when she couldn't I think he should have honored his commitment, and moved back to the Amazon with her. To not do so seems to reinforce the theory that he was only serving his own desires. If he had explained, to the tribe, that his people basically lived on a different planet, compared to them, and declined the offer, she likely would have become a mate to someone from her own tribe, and not had to suffer so much pain. I would think an anthropologist would have realised that.