If K-12 education is to include moral education, it must allow students to question or dissent from the moral education it provides without fear of punishment. Otherwise, it is indoctrination and thought reform, not education.
These theories basically divide society into two groups: oppressor and oppressed. If you are white, straight, male, and/or wealthy, you are an oppressor. If you are a racial minority, gay or trans, a woman or identify as some other gender, and financially not wealthy, you are oppressed. The objective of critical theory is to defeat oppressors and overturn the system that benefits them.