Yeah that is just plain old transphobic. A trans woman is not a "boy who wants to be a girl" it is a girl who wants to be accepted as a girl by herself and others.

You don't control what body or brain you were born with. For most people the brain's gender matches the body's sex, but for some it does not.

You are you, if you know that you are a girl or a boy or neither or both, then no one can say otherwise. Others can either respect you or not, but it means absolutely nothing about you.