This is an example of the Liberal Progressive ideas of moral reletivism. These are the people who teach that the Constitution is racist and a "living document" that must be reinterpreted. They teach that the Founding Fathers were misogynist, slave-owning, tax dodgers and we shouldn't listen to what they had to say.
Revisionist history is a tool of our nations destruction. Our children are not being taught what it means to be an American. They aren't being taught the meaning of freedom and liberty. They're being taught that their rights are gifts from the government like birth control and welfare and food stamps and free health care.