As a non-american, and as someone who is rather critical of american policy.
America was founded on a dream of a better world.
A lot of mistakes were made by the people who followed that dream. A lot of those mistakes were costly and violent. A lot of people didnt know any better. They were ignorant.
The blue devils were not evil men, but they were ignorant and stupid men, and they slaughtered natives quite cheerfully. They believed a lot of nonsense that we now know is simply wrong, and they commited genocide based on those beliefs.