That's identity politics. Only bigots think we're all human beings who all feel empathy for each other. No, our various racial/ethnic/sexual/identities are what separate us from each other and it's not possible for a white writer to get into the skin of a black character and write authentically about his/her lived experience. That same white, middle-class, progressive, university educated, English speaking American author is allowed to write about any other white character in history, from cave men to Rusian tzars, from Roman gladiators to Scandinavian vikings, but isn't allowed to write about any black person living or dead, real or imaginary.