During the heyday of Progressivism in the late 19th and early 20th centuries, the Progressive movement, while well-intentioned, was largely made up of and headed by white elites. As such, the movement as a whole suffered from the prejudices and assumptions of this group; namely, that the way white elites did things was the best/a better way to do things, and it was up to elite whites to improve the species as a whole through the use of research, reason, and knowledge. In this light, eugenics was the natural extension of that period's progressivism: if scientists could identify people who, by breeding, were inferior, then such defectives could be kept from ever forming.

I drew heavenly from Michael Willrich: Pox: an American Horror Story

I'm curious how you can academically define Left and Right in a useful way.