You mentioned brownshirts- the Holocaust was started by doctors- an MD signature on a piece of paper was the beginnings of “euthanizing” crippled children, developmentally challenged children, children with very low IQ.
About 100,000 over two years. It grew from there.
Life unworthy of Life.
The Nazi's got the idea from American Progressives in the early part of the Century.
When the world asked for justification on the Nazi eugenics programs. They cited the Buck v. Bell case in the U.S.