[DittoJed2]

I don't believe that the people who practised social Darwinism understood that the theory of evolution, as a scientific theory, cannot be used to provide a moral basis for actions.
Could be. Or it could be that evolution can not be considered philosophically neutral. The scientific method itself is, certainly. But Darwinism is a world view. Those becoming social Darwins were not being inconsistent with the implications of that worldview. Others who didn't take that path weren't being inconsistent either.

[Right Wing Professor]

But Darwinism is a world view

No, it's just a scientific theory. Dawkins made an excellent point in 'The Selfish Gene' that were the scientific ideas he was putting forward to be turned into a moral philosophy, he would reject them.