In California, the state laws that govern education require very specific kinds of diversity. For example, the curriculum must include "a study of the role and contributions of both men and women, Native Americans, African Americans, Mexican Americans, Asian Americans, Pacific Islanders, European Americans, lesbian, gay, bisexual, and transgender Americans, persons with disabilities, and members of other ethnic and cultural groups." And why not? They're all part of state history.
State law also forbids very specific kinds of discrimination.
No instructional materials shall be adopted by any governing board for use in the schools which, in its determination, contains: (a) Any matter reflecting adversely upon persons because of their race, color, creed, national origin, ancestry, sex, handicap, or occupation.
And why not? The U.S. Constitution arguably reflected adversely upon persons because of their race, as did a whole lot of speeches, Supreme Court decisions, and so on. So long as primary sources with antiquated assumptions about race and sex are accepted, there is no need for secondary materials that treat anyone adversely because of their race or color or national origin or sex or handicap or ... hey, wait a minute!