Dalthnock: I'm pretty sure "fully" transitioned people have been using their bathroom of choice for quite a while, now.
Depends on what you mean by 'fully'. If you mean they have been on hormone therapy, then it's entirely possible; however, bills like the one that got passed in NC don't make that distinction, and they require that surgery be done (more on that later).
If you mean to refer to people who have undergone surgery, then here's some fun trivia: a lot of people don't undergo surgery. There are a whole hell of a lot of reasons for that. First off, it's incredibly expensive and may not be covered under your insurance. Secondly, even if cost isn't an issue, sex reassignment surgery is the kind of procedure that can go horribly wrong in many ways.
Also, even if someone does decide to go through surgery in order to change their birth certificate (which states like NC do require for that sort of thing), there are no real guidelines about what kind of surgery is sufficient; the doctor may hold that enough has been done even if the surgery was for clearing one's sinus passages, meaning that someone may be in compliance with the law but still has unchanged genitalia.
Dalthnock: The point is, if a little girl is accosted by a man in a woman's toilet, she can scream for help... but the way they want to change it, if the man fondles the little girl & she screams for help, the man will be lauded as very brave & the little girl will be scolded for being intolerant.
Do you understand my concern?
No, because fondling of that nature is still very much a crime; laws allowing trans people into bathrooms doesn't grant everyone the bathroom version of Diplomatic Immunity for any sex crimes committed in the john.