Between the World and Me explores the author's growing awareness to the ways in which racial prejudice are deeply and systemically ingrained in society, and this book is Coates's elucidation of that experience, which he's sharing with his son.
While in Professor Heywood's class, Coates had the experience of realizing the story of Queen Nzinga, which he had held in high esteem and viewed with a kind of pride, is still about power dynamics and control of bodies. He comes to this lockturn moment when his professor matter-of-factly describes the "servant" on whom the queen sat while negotiating, and it makes Coates think about the way the state controls black bodies, too, and what he has in common with the servant, as a black man in America.
For Coates, it's a moment that shatters the illusion of romanticism that he'd previously assigned to the legend, referring to the story of Queen Nzinga as "my Tolstoy," meaning a work of emotional intensity and cultural pride that deals with the large themes of life. Coates realizes that systems of exploitative power are pervasive throughout history, and he ponders this idea in conjunction with learning more about the dehumanization of human beings.