Yesterday while picking up some groceries and assorted items, I required a trip to a public restroom that contained 10 stalls. As I took my seat I noticed nice shoes under the partition next door. Now, these shoes looked feminine, but frankly, I have no idea what the chromosomes or genitalia of that person were. I could not tell, even at those close quarters, if this person had a vagina or penis. For all I know, they might have been cursed with two penises or a persistent cloaca! They might have been XX, XY, or some other combination of DNA units. I don't know if this person was doing #1, #2, or something else in there.
All I know is that their outer appearance, based on shoes, was female. AND NONE OF THE REST OF THIS MATTERS ONE BIT WHILE I'M PEEING!
If someone presents themselves to the world as a woman, they get to use the women's restroom. And vice versa.