What the hell do people think there is to see in public washrooms? You may see a fully clothed person washing their hands. You may see the clothed back of a penis-equipped person standing at a urinal. If you try (bend over a little) you can probably see the feet of a person sitting on a toilet in a cubicle, maybe with trousers around their ankles. There is absolutely nothing sexual on view unless you have an uncommon fetish. No genitals, no breasts, no naked body parts or bare skin that you would not see anywhere else outside of the washroom.
Public washrooms are smelly. They are not the type of place that most men would consider a prime pick-up spot and hang out waiting for the "right" woman to come along. They are not the type of place where those with voyeuristic inclinations can expect to see anything other than clothed people doing normal every-day things. They are not the type of places where a rapist will have sufficient undisturbed time to plan and carry out an attack. Any person loitering in a washroom will immediately attract unwanted attention in a place where everybody else conducts their necessary business and leaves as quickly as possible.
If there is really any rational reason why a person would feel threatened or vulnerable or embarrassed while using a multi-gender washroom it has not been presented here.