I would heartily second Jonah’s reference to Chesterton’s Eugenics and Other Evils as proof of his independent-minded resistance to the progressive era’s worst excesses. It’s an extraordinary book, and Chesterton really saw how the various elements of the progressive worldview held together, and how the obsession with scientific (which in many cases was really pseudo-scientific) rationalization made the underlying assumptions especially clear. I think something similar can be said about the progressives of our own era: that some very important weaknesses in their worldview become apparent when they turn to scientific questions (a point I try to argue in my own—far far lesser—new book on science and politics).
Chesterton’s book is also a rich source of references and quotations that demonstrate just how explicitly anti-egalitarian and inhumane the progressives of his day really were. (This recent edition of the book, which also includes extensive selections from the writings of his opponents and critics is especailly useful in that regard).
And all this offers me another opportunity to recommend the chapter on eugenics in Jonah’s book to anyone who cares about the subject: it is extremely well done.