There have been many such groups deemed to be "unfit" in the history of biological genocide as there has been when the believed benefits of killing them are not explicitly biological but are benefits of political or economic or social advantage. There is a larger taxonomic grouping which includes all such morally nihilistic ideologies.
The original line of thought which Darwin took up, Malthusianism, was certainly based on a benefit to the upper classes, not on the basis of the alleged biological superiority of the survivors. If anything Darwinism made Malthusianism more dangerous because of its holding that the deaths of the "unfit" would be beneficial in the next generation.
The central depravity of the whole thing begins with the moral nihilism of intentional killing as an aspect of instrumental thinking. The further depravity begins with Darwin superstitiously believing that any selective factors which nature might use to kill off those who would be cut off from the future were discernible by science on the basis of human perceptions of utility and "fitness" when there was absolutely nothing that demonstrated that human selection had anything to do with what would happen in the wild. If anything the fact that humans found the variations they chose to cull out with slaughter would indicate the two things were, actually, NOTHING ALIKE. That a member of the British upper class came up with that massively arrogant idea doesn't surprise me for a split second. If a member of the beleaguered British poor or destitute were coming up with the idea I'd wonder if they didn't see things differently and a member of a minority discriminated against on the basis of race or ethnicity in Britain wouldn't come up with even a different idea.
Update: 2 Comments
If tomorrow a scholar found an Edison cylinder of Charles Darwin giving a speech advocating the mass execution of people he personally disliked, that would not change the fact that the reason the Nazis prioritized the murder of six million Jews was centuries of European Christian anti-Semitism. And your continued assertions to the contrary are bullshit Holocaust revisionIsm at best.
"Now moral relativism seems to be the most tolerant form of morality — you do what you want to do and I will do what I want to do. However, it actually leads to enormous intolerance because if there is no objective standard of morality, how am I going to show I’m right? And when that happens, it is the loudest, angriest, rudest voice that wins."
It works as a description of the error in letting the biggest assholes rule the internet discussion, as well.
Shorter Simels: "Nothing more than way too simple can be said."