> Nietzsche advocated what we would today call Social Darwinism
Not really.
https://en.wikipedia.org/wiki/Social_Darwinism Friedrich Nietzsche's philosophy addressed the question of artificial selection, yet Nietzsche's principles did not concur with Darwinian theories of natural selection. Nietzsche's point of view on sickness and health, in particular, opposed him to the concept of biological adaptation as forged by Spencer's "fitness". Nietzsche criticized Haeckel, Spencer, and Darwin, sometimes under the same banner by maintaining that in specific cases, sickness was necessary and even helpful.
In fact, Nietzsche experienced a number of health problems himself.
Social Darwinism is not an incredibly useful term (and it's interesting the extent to which the Stanford Encyclopedia of Philosophy buries it: I was going to try and find you a better reference and to some extent failed https://plato.stanford.edu/index.html), not to mention it's not a good concept, but that Wikipedia page is really not a good exploration of the topic. Nevertheless, note that Nietzsche is listed in the "proponents" section.
Social Darwinism, when used as a concept by people in practice, has never been about a rigorous application of Darwin's theory.
Not really.
https://en.wikipedia.org/wiki/Social_Darwinism Friedrich Nietzsche's philosophy addressed the question of artificial selection, yet Nietzsche's principles did not concur with Darwinian theories of natural selection. Nietzsche's point of view on sickness and health, in particular, opposed him to the concept of biological adaptation as forged by Spencer's "fitness". Nietzsche criticized Haeckel, Spencer, and Darwin, sometimes under the same banner by maintaining that in specific cases, sickness was necessary and even helpful.
In fact, Nietzsche experienced a number of health problems himself.