Apparently the only Indian he ever observed was one alcoholic hang-about-the-fort. He paints all Indians with that broad brush and only an uninformed idiot would consider it realistic. Try reading some Allan W. Eckert.
There is a lot of difference between a historian and a historical writer. If you want facts, the best sources are the reports of US Army officers of the time, who much of the time acted as mediators between tribes, while often disregarding “kill them all” orders from Washington.
But the fantasy approach leads nowhere.