Schlesinger was a New Deal and New Frontier liberal, which actually put him to the right of, or perhaps on the more patriotic side of, the modern multiculturalists.
Here are a couple of excerpts from his New York Times
obit, Arthur Schlesinger, Historian of Power, Dies at 89
[By Douglas Martin, February 28, 2007]
However liberal, he was not a slave to what came to be called political correctness. He spiritedly defended the old-fashioned American melting pot against proponents of multiculturalism, the idea that ethnicities should retain separate identities and even celebrate them. He elicited tides of criticism by comparing Afrocentrism to the Ku Klux Klan.
And later in the obit, we see this:
In 1991, Mr. Schlesinger provoked a backlash with “The Disuniting of America,” an attack on the emergent “multicultural society” in which he said Afrocentrists claimed superiority and demanded that their separate identity be honored by schools and other institutions.The novelist Ishmael Reed denounced Mr. Schlesinger as a “follower of David Duke,” the former Ku Klux Klan leader. The Harvard professor Henry Louis Gates Jr. caricatured Mr. Schlesinger’s arguments as a demand for “cultural white-face.”Mr. Schlesinger was nonplussed. He frequently described himself as an unreconstructed New Dealer whose basic thinking had changed little in a half century.“What the hell,” he answered when questioned by The Washington Post about his attack on multiculturalism. “You have to call them as you see them. This too shall pass.”