Holy Moley. Having just seen the film (we just got back), I am astounded at the utter vacancy of Scientific American's use of this argument.
Any fair-minded person who watches Stein's film will realize:
Stein or his interviewees say--on at least two occasions, and at some length, that Darwinism does not automatically lead to Nazism. The most elegantly stated, in my opinion, is the gentleman who acknowledges the time and space differences between Hitler and Darwin, and then he says something akin to "Darwinism is not a sufficient philosophy to lead one to Nazism, but it is a "necessary" one."
The film explicity states that not every Darwinist turns into a Nazi...but it does show how people like Margaret Sanger and Hitler freely used Darwin's ideas.
Additionally, the quote in question is used after the effect of Darwin's philosophy played itself out--in essence, the words used by Darwin that were adopted by the "pure race" advocates.
The quote takes up probably about 15 seconds of the film, after the evidence had been presented that Darwin's ideas formed the foundation for those actors in history.
In my opinion, this "objection" by SA, especially after having seen the flick, is incredibly weak.
Additionally, the quote in question is used after the effect of Darwin's philosophy played itself out--in essence, the words used by Darwin that were adopted by the "pure race" advocates.
For me, having read both Darwin, and having read some of the Nazi corpus on race theory, your description simply reinforces the fact that the film severely misrepresents Darwin.
Darwin never argued for "pure" human races. Indeed he forcefully argued in exactly the other direction. Darwin concluded for instance that humans are a single, highly variable species; that there is no way to sort humans into distinct races; that for any races one did nevertheless attempt to identify the variation within them swamps the differences between them, and that there are always an array of intermediate characters insensibly connecting all races. Darwin argued all of this in his [i]Descent of Man[/i] (in Chapter VII, "On the Races of Man"), and the Nazis adamantly rejected all of it.
The Nazis acted on the tenets of the race theories of Gobineau, Chamberlain, and the like, as explicitly set out by Alfred Rosenberg and others, that human races WERE distinct, that they originated so, that their racial purity (or that of the "aryan" race) should be restored. This was all incompatible with or foreign to Darwin's teachings and conclusions.