When transphobes say "I identified as a dinosaur when I was six, kids that age are too young to know they're trans!".

Nah, you didn't identify as a dinosaur. You didn't cry yourself to sleep because you couldn't figure out why you had no tail. You didn't feel an inexplicable sense of shame at your lack of claws. When you saw yourself in a mirror in a dinosaur costume, you weren't upset about all the non-dinosaur bits you could still see. When others saw the costume, you weren't brought to tears by them treating you like a child-wearing-a-costume instead of a real dinosaur.

You were playing make-believe. Kids do that. Kids also have genuine insight into themselves as no external observer can, and we should be helping them to explore that so that they can make better choices.

If your child told you that they were hearing voices, you wouldn't care that they were too young to understand schizophrenia. If they said that they had a wrenching pain in their gut, you wouldn't rage about "liberal doctors brainwashing children". Yet if a kid says "It hurts when people say I'm a boy/girl." suddenly the idea of treating that symptom becomes a conservative boogeyman.