And of course the Nazis got their inspiration for the doctrine from Margaret Sanger and other heroes of the Left here in the USA.
Don't forget Nietzsche. Eugenics was actually popular at the end of the 19th century, and a lot of the upper crust in this country believed it because it was "SCIENCE!"
They wanted reasons to believe they were superior, and so they seized on these Darwinian ideas of "survival of the fittest." Margaret Sanger and her abortion plague was founded more on this idea of controlling "Human Weeds" than it was on any concern for "reproductive freedom."