Our treatment of native Americans is right up there with the worst.

We can't undo it. All we can do is remember it and try to be better in the future for having committed the atrocities in the past.

For the last 50,000 or so years of our evolution, there was no word for genocide and crimes against humanity was a concept that we didn't grasp. In the last hundred years we have at least learned to question ourselves and try to make amends to some extent. The only thing that we can do that matters is to not do it again.

Films like Avatar like to imply that we have learned nothing and we will make the same mistakes in the future. I think they are wrong. There will always be individuals, even groups of individuals, willing to repeat the mistakes but I believe that humanity as a whole is good.