NZ's two historians specialised in Darwin:

       The best account of Darwin's views on eugenics and their development is John H Greene, Darwin as a Social Evolutionist'.  It is reprinted in Science, Ideology and World View, U. Calif. P. 1981. 
                The title should say Social Darwinist rather than Social Evolutionist. 
                Greene argues that Darwin took up the ideas of other people and tried them out, but was unable to decide how far to take the social Darwinist argument.  The logic seemed unassailable but he didn't like the anti-humanitarian conclusions so he was ambiguous in his statements.
        There is also a note by Richard Weikart in Isis vol 86, 1995, 609-611 'A recently discovered Darwin letter on social Darwinism'.   Darwin is pro-social darwinism in this. 

        Overall he wasn't a great public advocate of eugenics, but he seems to have been privately persuaded.

        What with skilful forgeries like the 'Lady Hope' furphy (depicting Darwin as having regained faith in a big way just before his death), perhaps someone will challenge this summary.  Meanwhile, it seems to be authoritative.  Now how is it relevant to the fight against "creationism"?

        "Creationists" fanatical enough to tell lies for God would be quite capable of misrepresenting what Darwin said about eugenics.  "Creationism" detests neoDarwinism (as do I, but on different grounds).  It tends 'therefore' to vilify Darwin.  This new attempt to align Darwin with Nazi eugenics is wrong on several levels, illustrating the depth of dishonesy characteristic of "creationism".