Until recently, Kosoko Jackson was considered an expert in the trapdoors of identity-related rhetoric. Jackson worked as a “sensitivity reader” for major publishers of YA fiction, a job that entails reading manuscripts and flagging them for problematic content. His own debut novel, A Place for Wolves, was promoted as an “#ownvoices” book, a hashtag attached approvingly to books in which the author shares a particular marginalized identity with his subject. (Jackson is black and queer.) He believed that, for example, women shouldn’t “profit” from writing gay men’s stories, as he tweeted last year. And he was part of a small...