Trying to Google this. The first 50 hits are creationist sites. And Gould wasn't a Marxist. There was some other Gould who was, but not the Harvard biologist. (He was a leftie, but not a marxist.) Still searching for this "quote" ...
Biological arguments for racism may have been common before 1859, but they increased by orders of magnitude following the acceptance of evolutionary theory.The non-creationist reference is here: Creation/Evolution Quotes. It's this:
Biological arguments for racism may have been common before 1859, but they increased by orders of magnitude following the acceptance of evolutionary theory. The litany is familiar: cold, dispassionate, objective, modern science shows us that races can be ranked on a scale of superiority. If this offends Christian morality or a sentimental belief in human unity, so be it; science must be free to proclaim unpleasant truths. But the data were worthless." (Gould S.J., "Ontogeny and Phylogeny," Belknap Press: Cambridge MA, 1977, p.127)