Anti-racism was neither solely nor primarily a Jewish invention. It initially arose through a radicalization of the abolitionist movement in the early to mid 19th century, its adherents being overwhelmingly of WASP origin. It then fell into decline, largely in response to the failure of black emancipation and the growing influence of Darwinian thinking in the social sciences. It was this half-discredited antiracism that Jewish immigrants, like Franz Boas, encountered in the late 19th century and the early 20th. With the rise of Nazi Germany, antiracism made a resurgence, and Jewish intellectuals certainly contributed to this resurgence for obvious reasons. But it was at all times as much a northeastern WASP cultural trait as a Jewish one.He's now back with more of this:
How did [Franz Boas's] views on race evolve over the next twenty years? This evolution is described by Williams (1996), who sees his views beginning to change at the turn of the century. After getting tenure at Columbia University in 1899, he became immersed in the elite liberal culture of the American northeast and began to express his views on race accordingly. [. . .]
From 1900 to 1930, Boas seemed to become increasingly liberal in his views on race, but this trend was hesitant at best and reflected, at least in part, a change in the audience he was addressing. As a professor at Columbia, he was dealing with a regional WASP culture that still preserved the radical abolitionism of the previous century. A good example was Mary White Ovington, whose Unitarian parents had been involved in the anti-slavery movement and who in 1910 helped found the NAACP. Boas was also dealing with the city's growing African American community and, through Ovington's contacts, wrote articles for the NAACP. Finally, he was also dealing with the growing Jewish community, who identified with antiracism partly out of self-interest and partly out of a desire to assimilate into northeastern WASP culture.
It's an outrageous distortion of history to suggest Jews supported antiracism "out of a desire to assimilate into northeastern WASP culture".
Most northeasterners, of any class, were never abolitionists (antislavery does not equal abolitionist), and even most abolitionists did not advocate anything approaching modern anti-racism.
No major constituency in America denied the existence of biological differences between blacks and whites when Boas immigrated, and advocating such views provided no quick path to social advancement (though obviously, at a deeper level, Boas was no doubt motivated by a desire to eliminate "anti-semitism").
It would have been very strange indeed for a physical anthropologist in 1890s America to outright deny the existence of race or obvious racial differences. What matters is the direction in which Boas differed from his contemporaries. And there's no question Boas was promoting "anti-racism" from the outset. Frost selectively quotes Boas's 1894 address "Human Faculty as Determined by Race", but even the excerpts chosen by Frost should make clear which direction Boas was pushing. Boas was not disinterestedly speaking race realist truth to an anti-racist American establishment, but lecturing Americans that no differences in civilizational potential had been proven to exist between the races of man, and insisting that any mental differences that existed could not be large, as the opening and conclusion make clear:
Proud of his wonderful achievements, civilized man looks down upon the humbler members of mankind. He has conquered the forces of nature and compelled them to serve him. He has transformed inhospitable forests into fertile fields. The mountain fastnesses are yielding their treasures to his demands. The fierce animals which are obstructing his progress are being exterminated, while others which are useful to him are made to increase a thousand fold. The waves of the ocean carry him from land to land and towering mountain ranges set him no bounds. His genius has moulded inert matter into powerful machines which wait a touch of his hand to serve his manifold demands.
What wonder when he pities a people that has not succeeded in subduing nature; who labor to eke a meagre existence out of the products of the wilderness; who hear with trembling the roar of the wild animals and see the products of their toils destroyed by them; who remain restricted by ocean, river or mountains; who strive to obtain the necessities of life with the help of few and simple instruments.
Such is the contrast that presents itself to the observer. What wonder if civilized man considers himself a being of higher order as compared to primitive man; if it is claimed that the white race represents a higher type than all others.
When we analyze this assumption, it will soon be found that the superiority of the civilization of the white race alone is not a sufficient basis for this inference. As the civilization is higher, we assume that the aptitude for civilization is also higher; and as the aptitude for civilization presumably depends upon the perfection of the mechanism of body and mind, the inference is drawn that the white race represents the highest type of perfection. In this conclusion, which is reached through a comparison of the social status of civilized man and of primitive man, the achievement and the aptitude for an achievement have been confounded. Furthermore, as the white race is the civilized race, every deviation from the white type is considered a characteristic feature of a lower type. That these two errors underlie our judgments of races can be easily shown by the fact that, other conditions being equal, a race is always described as the lower the more fundamentally it differs from the white race. This becomes clearest by the tendency on the part of many anthropologists to look for anatomical peculiarities of primitive man which would characterize him as a being of lower order, and also by the endeavors of recent writers to prove that there exist hardly any anatomical features of the so-called lowest races which would stamp them as lower types of organisms. Both these facts show that the idea dwells in the minds of investigators that we should expect to find in the white race the highest type of man. [. . .]
Although, as I have tried to show, the distribution of faculty among the races of man is far from being known, we can say this much: the average faculty of the white race is found to the same degree in a large proportion of individuals of all other races, and although it is probable that some of these races may not produce as large a proportion of great men as our own race, there is no reason to suppose that they are unable to reach the level of civilization represented by the bulk of our own people.