This lengthy piece at Quillette by Michael Robillard uses gender ideology as a case study about objective reality: The Incoherence of Gender Ideology.
He incudes this Dalrymple quote:
Political correctness is communist propaganda writ small. In my study of communist societies, I came to the conclusion that the purpose of communist propaganda was not to persuade or convince, not to inform, but to humiliate; and therefore, the less it corresponded to reality the better. When people are forced to remain silent when they are being told the most obvious lies, or even worse when they are forced to repeat the lies themselves, they lose once and for all their sense of probity. To assent to obvious lies is in some small way to become evil oneself. One’s standing to resist anything is thus eroded, and even destroyed. A society of emasculated liars is easy to control. I think if you examine political correctness, it has the same effect and is intended to.
This is how you subvert a nation and a people.