The argument is that African American students perform poorly in these subjects on average, and it impacts their grades and thus impacts their college admissions.
So the only way to even the playing field is to eliminate difficult subjects in high school, so that everyone gets near-perfect grades.
And that's a completely racist argument. The irony in the people pushing these ideas is astounding. They've basically taken an easy political out and instead of doing the hard work and realizing that African Americans can meet the same standards they've basically just said "nah they're too stupid so we'll lower our standards to make their grades look better."
So the only way to even the playing field is to eliminate difficult subjects in high school, so that everyone gets near-perfect grades.