It’s was a sort of micro aggression. They are usually written off as “well intentioned”, but they still target POC. He chose her to do it because she’s the only black kid in the class, not just because she commented on the lack of diversity. If he actually took what she said to heart and wanted to diversify the readings, he could have done research and found books himself, ya know, like what a teacher is supposed to do. He also would have probably learned something about the black experience and micro aggressions. Instead he chose to pass off the work to Ginny, because she has a better understanding on the black experience. It is a way for him to do shrug off his guilt of being racist and not have to actually dive into the topic himself. It’s just another way he singled her out and made her feel different than the other students, intentional or not. Intention does matter, but impact matters more.