Yes, 'sex' differences exist. Penises and vaginas exist. However, these organs are not inherently male or inherently female. There are female penises and male vaginas. Why does one doctor override the person and other doctors in this instance? What makes a penis or vagina all powerful over identity in this ONE small instance? What happened to bodily autonomy? Penises just happen to be typically on men. Vaginas just happen to typically be on women. That doesn't make it an absolute truth. Penises could have easily been originally categorized as male. Same with vaginas and being categorized as female. Sex, as two distinct categories that are black/white and binary, was created by people. It is not scientific. The existence of penises and vaginas is scientific. There is scientific proof that penises can be female and vaginas can be male (or neither/both/fluid/etc.) and that is scientific fact because trans* people exist. They exist. Their gender/identity is not. That is personal. The only reason people say penises are male is because of someone said, this will be this category and that will be that category. This includes all aspects of 'sex'. Just because they are typically one way does not make it an automatic truth. End of discussion.