Race relations in America is complex and often unsettling, to say the least. For hundreds of years, a racist view was taught among white families that black people were essentially animals, not humans, and therefore that slavery was the natural extension of that arrangement. That is evil in the truest sense of the word, and the effects of such an insidious narrative stretch into the present day. Which brings us to the 1920s. Locke's The New Negro is a response to the debates between Washington and Du Bois, and Locke's participation in that debate was actually acknowledged by Du Bois.
Essentially, The New Negro is a philosophy about the subconscious opinions of black people that were still held by the majority during the early 20th century. Locke argues against the idea that black culture should quietly submit itself to white culture. In that scenario, black people would earn respect for acting white. Instead, Locke argues that what really needs to happen is that the public needs to be reeducated about black culture, so that it can be seen as the folk culture that it really is.
His other major contribution in this work is the idea that art is the method by which black culture could be accessed by the white majority. Although it would be fascinating to hear Locke's response to the burdens of 'black face' entertainment on black people, in the 1920s, such arguments were still a long way in the future.