Indians took up arms against the United States and killed civilians as well as soldiers. If we forgave Geronimo why cant we forgive Robert E. Lee?
For certain the European settlers, cavalry, etc. did many atrocious things. Their wanton slaughter of the buffalo on which the indigenous populations were dependent was inexcusable and yes the Indians were treated abominably by some. Not all.
But neither were the Indians pure as the driven show either. They committed many atrocities on innocent 'white people' and also on each other. Warring tribes could be vicious, attacking, torturing, making slaves of members of other tribes long before they were even aware there were Europeans.
Sitting Bull along with Crazy Horse attacked and killed many Americans culminating in the massacre at Little Bighorn (Custer's last stand.) But he would be allowed to join Bill Cody's wild west show making him likely the highest paid Native American ever at that time.
The fact is history over all of recorded time is full of brilliance, beauty, noble acts, world changing events and also includes the cruel, savage, ugly. History is messy and those that preceded us viewed themselves and embraced cultures that we in our time and experience do not. To judge them by our experience, by our time is to do them a great injustice. We should know and understand all our history, the good, the bad, and the ugly.
Which is why this whole stupid thing of tearing down historical statues, monuments, other markers is so misguided and wrong.