So, Richard Henry Pratt was most noted for running a school in Pennsylvania that forcibly educated Native American children into "American" culture - i.e. to wash the native culture out of them in the name of assimilation into the now dominant culture of, basically, white people. The Australians ran a very similar gimmick on Aboriginal children right through to the 1950's.
We know today what a barbaric practice this is, but at the time he argued it by claiming that cultural assimilation was the best way to deconstruct segregation. And that is how he played the "not racist" card to his brazen white savior complex.
And honestly, we still get a lot of that attitude today. The country's full of people who would say that they're not racist in a heartbeat, but further examination would reveal that they're only colorblind when people of color walk, talk, dress, and act like them. It's definitely still racism.