This is a really good illustration of what sociologist call reification[1] - specifically of gender in this case. What the parent does is confuse their idiosyncratic views with an underlying essentialism in their conceptualization of the universe. It allows people to externalize their thoughts into concepts like reality, human nature, or 'just how things are'. The reason this is a good example is that the author shoots directly at the concept of a 'gender reality' without mincing words. Generally the tactic is to reword personal belief as grounded external knowledge using the copula, but it's an epistemological slight of hand. Like all magic tricks, once you know it it's hard not to unsee it.

1. Berger, Luckmann (1966) The Social Construction of Reality