Problematic Treatment Of Indians

In fact, the character Quanah Parker portrayed in the movie, was a real Comanche chief and was the son of a white woman, Cynthia Ann Parker and the Comanche chief, Peta Nocona. Cynthia was captured by the Comanche as a young girl and lived with them for many years. She was re-captured by the Texas Rangers years later and was given back to her white relatives. She was very unhappy, ran away at least once and eventually stopped eating and died of influenza.
Some consider this film a remake of The Searchers, both films directed by John Ford. Additionally, some claim that The Searchers was loosely based upon (or inspired by) the story of Cynthia Ann Parker.

Not at all. The Comanche were brutal. The film makes them look good.

I mean...all this is kind of par for the course for how Native Americans were generally portrayed in media of the time. I will say though that I thought the film did a surprisingly good job (again, considering when it was made) of actually not making the issue as black-and-white as just "Native Americans = unambiguously bad; whites = unambiguously good" as westerns of the time had tended to be. The white population really isn't presented as shining paragons of human virtue able to lord their natural superiority and civilised natures over the savage Natives - for the most part, they're openly racist, greedy, selfish, and small-minded with really only Jim and Marty being genuinely good people - while Quanah Parker at least was presented as intelligent, fairly well-spoken and even somewhat sympathetic. The film even, via the character of Elena and through the treatment of Running Wolf (not respecting his desire to stay with the Comanches, keeping him like an animal in a zoo for everyone to gawk at, palming him off to an obviously unstable woman, etc.), calls out the white population on how they are in some ways even worse than those they've deemed to be "savages". And across the white captives, you have one who doesn't want to return because she's ashamed, one who doesn't want to return because he's been raised as a Comanche and fully integrated into that society, and one who simply wants to stay with her Comanche husband and children. And the two who end up returning to white society, as I said, are used by the film to highlight the worst of said white society.

I'm not claiming that this is a great film that portrays Native Americans absolutely 100% respectfully because of course it doesn't, but it's what I'll say was probably fair for its day: dated and problematic in many ways now, but by the standards of the time, relatively forward-thinking.