I did a little googling on Kantorowicz in response to Hugo's discussion of Norman Cantor. It was going to be a comment, but it got out of hand. It's not research, exactly, but it was interesting.
I found this which seems to suggest that Cantor was using the term"Nazi" ideologically, rather than literally, but we don't today generally distinguish between belief-holders and party-card-holders in this regard:
Take, for instance, the Weimar-era scholars whom Cantor calls"the Nazi Twins," Percy Ernst Schramm and Ernst Hartwig Kantorowicz. The appellation is not entirely fair. It is true that they were both right-wing. Schramm spent much of the war as a historian attached to the General Staff; for a while, he was daily in Hitler's presence. Kantorowicz was a friend of Goering, and took care to have a swastika placed on the cover of the book that made his reputation. Still, Schramm was not a party member. His friend Kantorowicz was not eligible: he was a Jew who emigrated, to the United States, quite late in the 1930s. What ties them to the Nazi Party is the historical and even mystical support they gave to the doctrine of the"leader principle."
Not only did Kantorowicz -- an officer in the Prussian army, veteran of WWI and critic of the Weimar state -- emigrate, he did so because he was removed from his teaching post as a Jew. He argued that his Jewishness was irrelevant and that his work and views were in no way contradictory to the party, but was removed anyway.
Opinions that his early work was consonant with Naziism seems to be a rising tide since Cantor:
[Ernst Kantorowicz's Emperor Frederick the Second (1927)], a central monument of Weimar historiography and culture, resonated with Nazism in ways that the recent Kantorowicz industry has resisted recognising. . . . In addition to being stridently nationalistic and Nietzschean (in the sense of admiring the demonic), Kantorowicz's biography was racist and projected a medieval empire that was both expansionist and germanocentric and that could subsequently be appropriated by Nazi ideologists. (Significantly, Goebbels allowed the book a generous re-edition in 1936.) Finally, Kantorowicz's unpublished letters and notes from the time of the Nazi take-over reveal that, in the summer of 1933, he was ready to acquiesce in the view that the Nazis were legitimate vessels of the nationalistic ideals of the George Circle.
Obviously, this is a very delicate subject and I regret that my reading of Kantorowicz's work comes rather close - not in its underpinnings, but in its conclusions - to that offered some time ago by Norman Cantor. But nostra tota quaestio non est de re optata, sed de re facta: as history, this seems right to me. [Dresner translation, based on two years of HS Latin:"Our ultimate question is not about the views, but about the facts." Intertran suggests"Our goal is not what we want, but the facts." Corrections eagerly awaited]
On the other hand, I also found this which suggests that by the time Cantor was writing it should have been clear that Kantorowicz was no longer a Nazi, if he had been before:
Ernst Kantorowicz, an Eastern European Jew teaching at Berkeley during the 1940s and 1950s--and then dismissed for spearheading opposition to the compulsory loyalty oath--exhaustively explored this physicalizing of politics in his"study of medieval political theology," The King's Two Bodies. . . . In the context of Kantorowicz's own experience as a Jew exiled from Europe during the expansion of the Third Reich, one hidden agenda in his project was to demystify the spiritually rationalized totalitarianism invested in national politics--a totalitarianism, that is, effected through conflating spiritual authority with the person of the head of state, and the integrity of the nation with racial and ideological"purity." This conflation could be said to have reached its modern apex in the symbolically charged person of Adolf Hitler, but was also resurfacing in Kantorowicz's adopted nation, the United States, in the anticommunist discourse dominating the postwar period. Kantorowicz speaks euphemistically of the German 1930s and the American 1950s as dominated by"the weirdest dogmas... in which political theologisms became genuine obsessions defying... the rudiments of human and political reason." (viii) [emphasis added]
This raises interesting questions, which relate to the Irving/Kirstein discussion we're having: Even if a book is ideologically biased, or even just logically unsound, it can raise issues and sources which are worth serious consideration. We all use as sources works which we consider flawed; learning how to use them is integral to our training. But nobody accused Kantorowicz of abusing sources though mistranslation or distortion, only of using an ideological framework that was more contemporary than grounded in medieval reality. Both the analysis and the facts were vigorous enough to resonate and withstand decades of supplemental, competitive and challenging scholarship. That is not something we can say for Irving. At some point, though, he may turn to writing decent history, or repudiate his current views; at that point we should be willing to.... what? Forgive? It's erev Yom Kippur, and I don't know the answer to that question.