It fairly unusual to use the second-person voice rather than first-person or third-person narration in an essay. In this essay, Walker uses the second person to create a distance in the speaker between the self who is a character in the essay and the voice telling story. This distance, with the narrator seemingly observing himself living his life from afar, establishes a sense of detachment about what he is saying.
This distance and detachment help diminish the sense of pain and anger the speaker feels at what racism has done to him, his children, and other Black people. He can tell his story dispassionately using "you," because it is as if all that he records is happening to someone else.
By not focusing on his own pain and instead writing a flat, matter-of-fact narrative about his life, the speaker lessens the impact of emotions he is expressing. We feel the lengths he goes to to tamp down his emotions. In addition to using the second person, he speaks to himself in the imperative voice, ordering himself to do things, such as when he says, in an order to himself, "dispute this" when he wife tells him that his son has probably already gotten over the incident at school in which another student told him that people of his skin color are "stinky." It is as if he has so distanced himself from his pain that he is robotic at times, directing himself through rational actions that help him exercise self-control over inchoate rage.
The second-person narration in this racial incident with the son allows the narrator to both express the deep anger he feels and remain distanced from it, as when he says of the child who hurt his son's feelings,
tell your wife you are twisting off his tiny, five-year old balls.
This utterance is deeply enraged, but the second-person voice helps both the speaker and readers experience distance from the emotion.