I hope its okay to raise some points against the logic in the "next logical step". Social Darwinism (from IOTL) were not all nazis and eugenics. Peter Kropotkin points out in the book "Mutual Aid: A Factor of Evolution" (1902) that Darwin didn't define the fitest as the the strongest. Its far from all the strongest and the best that survives. Many anymals survives and evolve as spices through cooperation. Humans too. Or in his words "struggle is replaced by co-operation." Its arguable that we don't need to kill the "unfit" and its arguable more "profitable" to be humane and rehabilitate. The mentally ill, physically deficient and socially backwards have all used precious resources by growing up its a waste to not rehabilitate them into productive participating members of society Or so the argument were before the first great war IOTL. This is setting aside the logical fallacy of Social Darwinism that "natural order" is always somehting good. I hope this gives some good insight for ITTL development of this. Eugenics don't have to be anything stranger than IOTL EUTHENICS in a liberal society.