Darwinism leads to social Darwinism
Social Darwinism is a group of political and sociological theories that generally view human "races" or classes that are in constant competition, with some groups possessing superior traits. It may also include advocating politics that promote the "superior" group's interests. Apologists sometimes blame racial theories of social Darwinism, eugenics, the actions of Adolf Hitler on Darwinism:
- "In other words, racism and then genocide is the logical outworking of Darwinism.[...] As horrific as that would be—using retarded people as lab rats or for food—Darwinists can give no moral reason why we ought not use any human being in that fashion."
Hitler made some claims about the struggle for life and racial theory, particularly in terms of prescriptive policies, but these are not part of evolutionary theory, which is strictly descriptive. Those would claim that social policies should be justified by evolution forget the is-ought problem, which says prescriptive claims cannot be based entirely on descriptive propositions. Just as Darwinism does not forbid misusing people, it does not encourage it either. Adolph Hitler required additional moral judgements, such those he took from Norse mythology and Christianity, to justify his actions.
Almost all scientists accept evolution but virtually none accept social Darwinism. This shows that it does not necessarily lead to social Darwinism.
So called "Social Darwinism" originates before Darwin published his ideas! It goes back to at least Herbert Spencer's 1851 Social Statics and 1852 A Theory of Population. The Origin of Species was published in 1859. Spencer originally considered species to originate through Lamarckism, not natural selection.
"“A generous poor-law” is openly advocated as the best means of pacifying an irritated people. Workhouses are used to mitigate the more acute symptoms of social unhealthiness. Parish pay is hush-money. Whoever, then, desires the radical cure of national maladies, but especially of this atrophy of one class, and hypertrophy of another, consequent upon unjust land tenure, cannot consistently advocate any kind of compromise."
- — Social Statics, 1851 
"For, necessarily, families and races whom this increasing difficulty of getting a living which excess of fertility entails, does not stimulate to improvements in production—that is, to greater mental activity—are on the high road to extinction; and must ultimately be supplanted by those whom the pressure does so stimulate."
- — A Theory of Population, 1852