On the link between Friedman and social darwinism this is very clear, no doubt there is much else in the literature
Elegant Tombstones: A Note on Friedman's Freedom quick view
C. B. MacPherson Canadian Journal of Political Science / Revue canadienne de science politique, Vol. 1, No. 1 (Mar., 1968), pp. 95-106
''The first thing that strikes the political scientist about Capitalism and Free- dom is the uncanny resemblance between Friedman's approach and Herbert Spencer's. Eighty years ago Spencer opened his The Man versus the State by drawing attention to a reversal which he believed had taken place recently in the meaning of liberalism: it had, he said, originally meant individual market freedom as opposed to state coercion, but it had come to mean more state coercion in the supposed interest of individual welfare. Spencer assigned a reason: earlier liberalism had in fact abolished grievances or mitigated evils suffered by the many, and so had contributed to their welfare; the welfare of the many then easily came to be taken by liberals not as a by-product of the real end, the relaxation of restraints, but as the end itself. Spencer regretted this, without offering any evidence that market freedom ever was more basic, or more desired, than the maximization of wealth or of individual welfare. Professor Friedman does the same.''