I suggest that you read, or re-read the Descent of Man. It is an example of a man making poor use of his own scientific work. Origin of Species was based on a lot of grunt work, which made his conclusions persuasive. But the second book does not rise to the same level, is based more on prejuice than observation, and the language IS racist.
I suggest you read it, because while Darwin played with the idea of applying natural selection to humans, he dismissed it as immoral (not “sympathetic”), stating that the sympathetic society will be the stronger one and thus win out over the society that isn’t. Thus Darwin’s belief is that eugenics will harm a society. Galton is the one you should be looking at.
“The aid which we feel impelled to give to the helpless is mainly an incidental result of the instinct of sympathy, which was originally acquired as part of the social instincts, but subsequently rendered, in the manner previously indicated, more tender and more widely diffused. Nor could we check our sympathy, even at the urging of hard reason, without deterioration in the noblest part of our nature.”