You have to consider what was happening on this continent since the Revolutionary War. The need for expansion and methods to do it were due to the circumstances of those times, not 21st century reparation concepts.
I won’t defend Sherman’s philosophy on the matter, but at the time, the Indian was a serious obstacle to expansion. The American Indian had peaked in the Stone Age and to think that the progression of the European invasion and subsequent battles wouldn’t happen is silly.
Of course, many consider that happened was wrong and the American Indian was the victim of Manifest Destiny or genocide, yet conflict was unavoidable. How could you leave some of the vast areas of this country to the Indian to continue to live the life they knew and develop everywhere else? That wouldn’t work either.
When you research history and find a group conquering another culture, you never see where the conquerors tried to assimilate the conquered people into their society as America did. It may not have been perfect or politically correct, but that was the attempt.
Sherman, Sheridan, Custer, Crazy Horse, Gall, Sitting Bull and many other leaders of those cultures fought for what they believed was right. There was no wrong side in that battle, it was inevitable.