But we are talking about the Christian Right in general, not just you. There is no doubt that various efforts are being made across the country to "tone down" the discussion of slavery in various ways and, as far as I am aware those efforts are coming from the Christian Right. Why?
I think you are mistaking a couple things
From what I have seen and read, virtually no Christians, even conservative ones, are seeking to abolish the discussion of slavery in schools, or even to "tone it down" (mislead)
What some Christians are doing, is seeking to prevent radical, leftist ideologies from hijacking history and social studies curriculums, in order to push political, and ideological agendas.
As James Lindsay accurately points out "Leftist activism is happy to take direct wins whenever it can get them, but that’s not always possible. When it can’t get direct wins through the front door, it is also more than happy to get its wins through the back door by exploiting what we can call an action-reaction dynamic. As an act of dialectical political warfare, which is their battle logic, Leftist agitators will provoke a reaction, control the framing around that reaction to a watching audience, and use the reaction as justification to advance their cause. This strategy was articulated by Saul Alinsky as “your enemy’s reaction is your real action,”
Action: In this instance, leftists push CRT-adjacent, Neo-Marxist concepts in schools (the oppressor-oppressed dynamic, that whites are inherently racist, that the country is "systemically racist", that historical record or empirical truth is secondary to 'lived truth', that the country was actually founded on slavery [1619 Project], that whites need to feel shame, guilt, and humiliation for their 'crimes', and that reparations and punishment are justified, etc.)
Reaction: Parents, other educators, and even politicians object to this. They try to pass measures in school boards, or even enact legislation to prevent radical ideology from getting pushed in classrooms.
The leftists then frame the reaction as "you just want to prevent kids from learning about slavery"!, or "you just want to promote right-wing ideas in the classroom"!!!!
I suggest watching this lecture