What to do with the racist "thinkers" of the past?

One of the African-American commentators that I often check in with, Charles Blow, had a timely reminder about Abe Lincoln: Tweeting on Lincoln's birthday, Blow writes "He signed the Emancipation Proclamation. He was also a bonafide white supremacist."  Blow also included the following text from the famous Lincoln-Douglas debates:

Somewhere else, Blow had argued that it is not inconceivable for a person to sincerely believe there should not be any slavery or mistreatment of people and also sincerely believe in the supremacy of their own kind.  We humans are capable of way worse, we forget.

Today, I was reading a book in which the author notes that the political philosopher David Hume was no different.  A quick Google search turns up more than I wanted to know, like this one that Hume wrote about 250 years ago:

“I am apt to suspect the Negroes, and in general all other species of men to be naturally inferior to the whites. There never was any civilized nation of any other complection than white, nor even any individual eminent in action or speculation.”

Any complexion other than white!

Did these "enlightened" Europeans even forget their tiny bit of interactions with the Moors?  Had they not even heard about the awesomeness of China or India?  Or Egypt? Or ...?

The more I learn, the more I am shocked at how awful the past had been.  Of course, to many hundreds of millions, like the Dalits in India, such ill-treatment is not stuff from the past, but is a continuing horror story.

The consolation is that at least today things are nowhere as bad as they were in the metaphorical yesterday--despite the best efforts of the supremacists in the US, in the old country, in Hungary, in ...

But, seriously, Lincoln too? :(