The Sioux were a coastal Carolinas Tribe with a serious distaste for English people so they kept moving west......moving west and conquering anyone in there way.
Ed McGaa is a Sioux, Marine pilot in VN war. Now deceased.
I spoke with him at the Crazy Horse Monument and bought his book.
His take on things was "The stronger culture conquered the weaker culture".
That was his justification of what the Sioux did to other tribes and what happened to the Sioux from the whites.
I dont think he was that well liked in Sioux circles though it seems he did a lot to keep their culture alive. His books are great....I know he instilled in me an education of who they are and why they should be respected.