Biology is not my strongest subject either but if you check into it you will find that there is more to it then the xx and xy at birth.
The XX or XY is determined at conception...not birth.
The XX or XY chromosome pairing determines gender - no ifs, ands, or buts.
Hormone imbalances do not change genetic material, but may change physical characteristics.
One does not have to have a PhD in biology or genetics to understand the difference between a boy and a girl.
If people recognize that something is not their strongest subject, I encourage them to try to educate themselves to improve their knowledge on the subject - or at the very least, listen instead of speaking about things they have limited knowledge of. (I believe we were born with 2 ears, but only 1 mouth, for a reason.) It is better to appear an idiot, than to open one's mouth and remove all doubt.