I don't recognize this "Darwinism" you keep talking about. I've been reading posts by FR members that other people have labeled "Darwinists" for years, and I've yet to hear anyone call for eugenics or the destruction of Christianity. If you can tell me how to distinguish people who accept the scientific theory of evolution from what you call "Darwinists," maybe I can answer your question.
Do a search for Francis Galton and Leonard Darwin, also do a search on Charles Darwin and Christianity.