In the view of the author, the scads of 'dark' babies (especially those black ones) that will be born. He despises them with every ounce of his being.
Well, I’m not sure what the author intended. Liberals - even most journalists, these days - seem to have tunnel-vision about a lot of issues. They don’t think much for themselves, and swallow ‘party-lines’ and directives from management whole.
(They’ve been trying to whitewash Margaret Sanger recently, but you can still find her veiled and double-speak arguments for Eugenics. I’m sure that nobody in Sanger’s day missed the point):
https://www.nyu.edu/projects/sanger/webedition/app/documents/show.php?sangerDoc=239501.xml