A few years ago I read a western tale involving the basic trope of settlers versus Indians. Afterward, I checked out the reviews and the writer had gotten grief from some reviewers because a Native American character who was treated decently by a white woman turned around and brutalized her. One particular reviewer clearly considered this a racist characterization. I didn’t see anything racist in it, particularly not when I looked at all the characterizations in the story.
In fact, I think some of the negative reviewers were the ones being racist, although in a very subtle and convoluted way. I think that many of the negative reviews came from folks who, not only carried a healthy dose of disgust at the way European settlers so often treated Native Americans, but also accepted the “noble savage" myth. With that viewpoint, any Native American character has to have an innate decency to match against and call attention to the brutality of the “civilized” white men. One problem with this viewpoint is that the noble savage myth is indeed a myth, whether you're talking about American Apaches, African Bushmen, Australian Aborigines, or European Cro-magnons. None of these peoples, or a thousand other tribal societies, lived by some idealized civilized code of conduct. Not only would it have been foolish for them to do so, but each was a completely realized and fully developed culture of its own, which did not necessarily value the same things as other cultures.
The worst part about this approach is that it actually diminishes those it seeks to promote. It turns them into less than full humans, draws them more as stereotypes (although a positive stereotype) than as living, breathing people. The fact is, as I've argued before, the Native American tribes were completely and fully human in every way. That means they were capable of great bravery and great treachery, of innocence and evil, and of kindness and savagery. They loved and they hated. Their culture taught them different ways of dealing with the world than my culture has taught me. And some of them, like with any group of humans, were just plain nasty sons of bitches.
It is not racist to have a Native American character who is a villain, no more than it’s racist to have a black character who is a criminal. Of course it is a problem if “all” of your Native Americans are villains, or all your black characters criminals. It’s also completely unrealistic. It’s also unrealistic, however, if all your Native Americans are depicted as noble savages. It diminishes a people if you turn them into stereotypes, even if the stereotype is generally positive.
In the story I’m talking about at the top, the “kind” white woman was a Christian woman who had good intentions but who was treating the “Indian” character more like a wayward child than a complete and complex human being. What the story really showed was that a mixture of naivety and a holier-than-thou attitude can get you hurt.
This whole issue raises another point. You can’t judge a writer’s attitudes from the depiction of one character. In a realistic world, any single character, of any ethnic type or any gender, could be a villain or a hero. Realistically, they’ll probably have some aspects of both. They’d show the traits that belong to all of humanity by virtue of our common biological origin.