Poignant quotes from “The Rise and Destiny of the German Jew” by Jacob R. Marcus, PhD, which was published in 1934:

“The most highly centralized and organized states of the late Middle Ages were the French and English states, created by peoples of hybrid descent. The poorest, most loosely organized state, was the unwieldy Germanic Holy Roman Empire. The first large organized German state was not welded together till 1871. The boast of a Nordic genius for political and military leadership finds little support in Teutonic history. 

We see, thus, that there is no indication whatever that race crossings are detrimental to the events of civilization. On the contrary, all the evidence seems to indicate that it is in just such areas where diverse peoples meet and mingle that civilization moves onward most rapidly. Culture has never been localized in any particular area where only a single racial group perseveres in its purity.

It is the resultant of diverse environmental and historical factors, and the areas in which it has developed from one level to another have shifted constantly from century to century and from land to land. More often than not it has drawn upon Mediterranean and Asiatics sources. As far as we know, it has been social organization and physical background which have made for civilization, rather than “blood.” Europe has certainly not suffered from its admixtures of diverse racial elements. The whole situation can be aptly summarized in the words of the very cautious Hankins: “It can be stated with comparative safety that the world’s geniuses have been with rare exception cross-bred, in areas of race mixture.”

The same argument applies to Germany itself. The Germans of modern days have become a great cultured nation and the civilizing influence not because of their Nordic stock but largely because of geographic and historic conditions. Like all other peoples, the racial amalgam that is today Germany borrowed heavily from all previous social orders and civilizations and showed a lusty ability for assimilation, the very trait that is found so objectionable in the Jews. It's typical culture reveals itself most distinctively in central and south Germany where there was a fusion of it least the Nordic and Alpine strains.  The Franconian, Suabian, and Thuringian lands – where German culture first manifested itself – are not areas of Nordic types.” —From pages 60-61.

“If this were not sufficient to condemn the Jews, the German racists add another charge: the Jews are different because they have a “consciousness of blood and kind.” This is bad when Jews possess it – it becomes a virtue, ostensibly, when Germans possess it.

 It is a curious phenomenon that not only Jews may be “Jewish” in the minds of ardent Nazis. Anything which the Nazis dislike becomes “Jewish”, whether it be men with hook-noses and earlocks, or department stores, or the horizontal type of architecture. Noted Catholic leaders like Erzberger and Adenauer become “Jewish” when they arouse the ire of the Nazis.” —From page 64