“Rather than celebrating the ballet dancing boy or football mad girl, we instead tell the football lover if she feels more like a boy then she probably is a boy and get boy ballet dancers to declare themselves female.”
There are many holes to be picked in this argument but let’s start here.
Are you honestly suggesting that men who are ballet dancers must all feel themselves to be women at heart? Or that women who enjoy football must, deep down, feel like men — *be* men, in fact? Or that people’s notion of their own gender is so flimsy and oscillating that it might fluctuate simply because they “won a race” or “baked a cake”?
Conflating hobbies and interests with gender is by far the most absurd thing in an argument not shy to invoke the absurd.
Your concern about “personal inclination [becoming] the arbiter of truth is an interesting and potentially legitimate one, but this is not the way to win that argument.