Arguably, his ideological work An Idea Conquers the World is more important for study and revisionist narratives. Kalergi excuses both H. S. Chamberlain and Gobineau*, distinguishing their racialism from anti-Semitism. He actually met Chamberlain at Bayreuth and had the opportunity to study him closely. I wouldn't be surprised if Kalergi made a similar gesture on behalf of Wagner (he was on good terms with Cosima and her family). He was also an admirer of Nietzsche and claimed him as one of the early pioneers of Pan-Europeanism. He only omitted Luther, but Kalergi distinguished Hitler's anti-Semitism from the traditional religious hatred. Thus, Kalergi has inadvertently furnished arguments against the Sonderweg myth, absolving them of blame for Hitler.

Curiously, he dated Hitler's war "against" Europe from 1919 (signing of Treaty of Versailles), as opposed to 1933 (rise to power) so he didn't succumb to the fixation on details one finds in conventional historians. In this light, it'd be appropriate for Christians to portray Jesus' incarnation as a lifelong struggle rather than starting from his last few years or his death.

And his work Anti-Semitism Throughout the Ages, while full of misleading apologist arguments, is probably pure dynamite in the right hands. At one point, he practically indicts the Western democracies, portraying their "help" rendered to Jews as a largely unsympathetic gesture (which Hitler himself drew attention to in his January 30, 1939 speech) and instead characterizes it as a feeble protest against Hitler's anti-Semitism. Today we see a similar spectacle occurring with Ukraine and Russia.

As for his claim in Practical Idealism about the artificial selection process for future Jewish leadership, there are actually good grounds for his assertion. It's just a question of whether it will be Zionism or (Aryan) humanism which wins the struggle for the Jewish "soul" (see Dietrich Eckart's The Earth-Centered Jew Lacks a Soul). Kalergi's personal list of meritorious Jews blurs the line between the two factions of Jewish greatness (material/civilizational vs spiritual/cultural expansionism).

Of course, Kalergi inclined towards Zionism, and his father naively believed Jews could be assimilated into the West without renouncing their traditional religious/pragmatic values. If one regards a people as an enemy of Nature, one must either convert or destroy them. (Rousseau) They cannot possibly live at peace with them and arrive at a mutual understanding.

*both of whom were regarded by Hitler as mandatory reading for participating in debates on the racial question