Never mind the fact that, even if social Darwinism necessarily followed from Darwinism, that would not prove that Darwinism isn't true. Such an argument, though valid, is unnecessary because, as it just so happens, there is no causal relationship between the two. Social Darwinism is a flagrant example of what we call the "is-ought fallacy", a faulty inference that, since something is a certain way, we therefore ought to be that certain way. It is a fallacy because we can not logically derive "ought" from "is". If a person observes a bird that is eating some red berries, he would be foolhardy to think that he ought to eat them as well; the red berries could easily be digestible for birds but poisonous to humans. Equally absurd is the suggestion that, since nature selects by a process of "survival of the fittest", humans must therefore model their social policies on the same theme.
Moreover, "survival of the fittest" (a term coined not by Darwin, but by Herbert Spencer) is not even regarded as an accurate description by modern biologists. Does Stein think that scientists have made no further inquiries into the subject of evolution in the 150 years since On the Origin of Species was written? Even if they had not, Darwin himself understood perfectly well that evolution by natural selection is a non-teleological process (that is, a non-goal oriented process). In other words, evolution does not work to bring about a super-species that is superior to all other species; fitness only refers to a species' ability to survive, not its inherent worth. Thus, Scriptulicious's pet ferrets are every bit as well-adapted, and therefore "fit", as Scriptulicious himself.
Finally, consider the following short film, and how every person, every race, every nationality on this planet has a common ancestry. There was actually an Adam and Eve, but the real Adam and Eve differ from their biblical counterparts greatly, indeed they never even knew each other. We inherit our mitochondrial DNA from our mothers, and we can trace markers in our mitochondrial DNA to a "mitochondrial Eve" who lived about 150,000 years ago in modern-day Africa. We inherit our y-chormosome DNA from our fathers, and we can trace markers in our y-chromosome DNA to a "y-chromosme Adam" who lived about 60,000 in Africa. These facts are coupled with archeological evidence of the rise of civilizations and with our knowledge of the historical climatological conditions that would have forced our earliest ancestors to migrate from the cradle of humanity. The multifarious faces of humanity arose as a single species, a single race, from out of Africa.
It is serendipitous, I think, that Lincoln and Darwin share their birthdates. At Gettysburg, Lincoln eloquently stated that "our fathers brought forth on this continent a new nation, conceived in liberty, and dedicated to the proposition that all men are created equal." Thanks to Darwin, we now have a knowledge of evolution and genetics which prove this proposition of equality.