"the irrationality of the Nazis' hatred of the Jews'"

First, I think Stone's attempt to put "Hitler in context" must surely address the anti-Semitism that was rampant in Europe? The Nazi's and indeed Hitler's anti-Semitism, didn't arise in a petri dish.

Second, the so-called 'Sub-Humans' (Untermensch) that the Nazi's were interested in exterminating, included the Slavic races just as much as Jewish people (disabled, travelers etc.). But as JtS says, targeting the untermensch at home and in conquered lands, was just the first step in world purification.