This backlash started, not with CRT, but with Common Core requirements.
When they saw how disastrous things like sight words were and as for common core math, well, here's a video to show some fun that parents deal with:
Not just the way common core requires math to be done, but the way they skip around from fractions to multiplication, all I see it doing is confusing my children. Sight words have been proven to be less effective than phonics especially in children with special needs and/or cognitive delay. And more often than not, we end up reteaching kids how to do the math that we learned. They understand the math that we learned much better than the math they are learning in school.
Like I said, I'm okay with us looking at our history book and pointing out that America was built on the backs of slaves that got nothing from it. I noticed that when my kiddo was quarantined that they really did a lot to beef up the curriculum around Native Americans, and I got to learn a lot more about the native groups that lived here prior to Europeans coming in. I think that is a really cool addition to the curriculum.
The problem I see is that while they are killing it in the social studies area, they don't even come close to effective math and reading curriculums. Most of the parents that I know have a much bigger problem with the way they are teaching math, than them teaching CRT. And this is where I get really cranky, because often times when people report that parents were seeing what their kids were being taught and they got upset, I really do wonder how many parents were getting upset over other aspects of the curriculum, but CRT makes a way better story than parents being mad about how kids are being taught to divide.