The following passage mentions African-American abolitionist Frederick Douglass, but the bold's figurative, possibly racist meaning eludes me.
That tap on the shoulder, metaphorical or not, Will Marion Cook came to know well when he returned to America. He tried to make his name as a violinist, advertising himself improbably as a "musical phenomenon performing some of the masterpieces upon his violin with one hand." Making little headway, he then formed the William Marion Cook Orchestra, with Frederick Douglass as honorary president. At around the same time, Cook wrote, or began writing, an opera based on Harriet Beecher Stowe's Uncle Toni's Cabin. Most significantly, in 1893, he went to Chicago to participate in the World's Columbian Exposition, a momentous event at which America declared its new status as a world power. In an effort to counteract the stereotypes of black savagery that figured in some of the fair's displays—crowds flocked to watch and hear the African drummers of Dahomey Village—Douglass organized a Colored People's Day, which aimed to affirm the nobility of the black American experience. Newspapers mocked Douglass by speculating that watermelons would be sold in bulk. [Bold mine]