What happens when you don't have an objective reference standard? How can you test hypotheses? For example, to say that some substance has a temperature of 135 degrees Kelvin only has meaning because 0 degrees Kelvin is a reference standard and the gradations of degrees are defined as well.
What does it mean to claim that you are "gendered" as a man or a woman? In our world of zillions of genders, what is the reference standard against which we measure gender? If it is your say-so and a biological woman who, without any surgery or drugs, is a man because she says she is, why does she then need the surgery? She's already a man by definition. The changes she is making to her body are not part of our definition of gender at all.
If there is no objective reference standard for man and woman, then gender is simply sexual preference. It's a definition of what gets you off. If I get off to looking at pictures of muskrats while rubbing raisins on my chest, then I should be given my own gender and pronouns if I say it is a gender. And I do.
My pronouns are muskx / musrax.
But if I do get off like that and I do define that as my gender and I do demand you call me by my muskratty pronouns, how is that different from a fetish? A difference that makes no difference is no difference. This, the societal endorsement of ever more bizarre fetishes, is what eventually happens when you abandon objective reference standards.
If 0 degrees Kelvin is defined solely by self-reference or arbitrary feelings, then the entire Kelvin temperature scale is meaningless. It is then useless for drawing conclusions about the world around us.
Sort of like gender.