"A doctor takes one look at us and makes a guess about what our gender identity will be: 'Well, I see a penis, so I think that this baby will grow up to be a man. Did I get it right?' If you’re cisgender it means that the doctor guessed your gender identity correctly at birth, and that you actually like the letter that the doctor put on your birth certificate when you were born."
ADDED: Interesting — unintentionally revealing? — use of the word "like." Not liking something doesn't make it untrue. If it's just a question of not liking it, Jacob Tobia doesn't have a compelling argument.