Explanation: The US has a horrible record with regards to actually upholding its treaty obligations with Native American polities. Especially in the second half of the 19th century, in which treaties rarely lasted a decade before the US broke them or forced the issue with a new war.
What sticks in my mind is always General Sherman's career after the Civil War. General Sherman, despite doing good work in whipping the slaver scum, was not humanely inclined towards the Native Americans. He was one of the architects, even, of the buffalo exterminations which sought to starve out any Native polity which refused sedentary agriculture on what little reservation land they were left with - so not exactly a paragon of humane behavior.
But even he regularly expressed disgust and disdain for the violence and lawlessness of white settlers towards the Native Americans. Mr. "War is cruelty, and you cannot refine it" was disgusted - because those white settlers had no notion of respecting any law or treaty that was made, whether made by them or by the Federal government. Certainly not out of a surfeit of sympathy towards Native Americans, but because even by the standards of an unjust time, the behavior of white settlers on the frontier was deeply fucking unjust and arbitrary.
