Influenced by the strict categories of so-called racial science, some American elites as far back as the 1910s emphasized the cultural differences of immigrants as a defense against the flattening effects of mass culture.
Menand quotes Randolph Bourne's July 1916 Atlantic Monthly essay "Trans-National America":
"Already we have far too much of this insipidity--masses of people who are cultural half-breeds, neither assimilated Anglo-Saxons nor nationals of another culture... Letting slip whatever native culture they had, they have substituted for it only the most rudimentary American--the American culture of the cheap newspaper, the "movies," popular song, the ubiquitous automobile.
Bourne's reference to "whatever native culture" immigrants possess is quite consumerist. It foreshadows present lovers of diversity who act as if diversity only means exotic food, clothing, and music.
Bourne also provides a very contemporary-sounding condemnation of the "imposition of values":
"If freedom means the right to do pretty much as one pleases... the immigrant has found freedom, and the ruling element has been singularly liberal in its treatment of the invading hordes. But if freedom means democratic cooperation in determining the ideals and purposes and industrial and social institutions of a country, then the immigrant has not been free, and the Anglo-Saxon element is guilty of just what every dominant race is guilty of in every European country: the imposition of its own culture upon the minority peoples.
Multi-culturalism is simply old racial science plus egalitarianism. Thus, it often retains the view that race is essential and all else is accretion. In the words of Horace M. Kallen, "men may change their clothes, their politics, their wives, their religions, their philosophies, to a greater or lesser extent; they cannot change their grandfathers. Jews or Poles or Anglo-Saxons, in order to cease being Jews or Poles or Anglo-Saxons, would have to cease to be."
The belief that ethnicity is more enduring than marriage, philosophy, or religion seems to have endured to the present day. It is a correlate of a materialistic society that holds the human genome to be more real than the individual, even more real than God.
This supposition is why a certain poor excuse for an Irishman, who runs some sissy-named organization called the Shamrock Club, can object to Holy Week trumping St. Patrick's Day festivities. He was able to say, "Actually, you’re born Irish first, and then you’re baptized Catholic."
Horace Kallen would approve, though St. Patrick certainly wouldn't.