But that's the opposite of his position.
Whether a person agrees with the argument or not, his stances is that some of the material in the course is obscuring Black history by spending course time and resources focusing on other issues like LGBTQ+ interests. He has pushed the College Board to revise the course to focus more solidly on the history of Black communities in the US.
You might reply that LGBTQ+ is part of Black history, and that's fair, but it's important to recognize that DeSantis is actually arguing. Not against Black history but against a course that he believes is insufficiently focused on exactly that.