You're kind of missing the point. They're not even trying to "keep prostitutes from expressing themselves" they are keeping prostitutes from being in a commercial business with a bunch of horny guys with money; with the same types of powers they wield to keep people with illegal addiction issues becoming pharmacists.
They are regulating this in commercial venues because they can.
e.g. If your Mom is sick, and sneezes all over the food she's about to serve you, there is nothing government can do about it.
They CAN (and do) however, regulate health practices that go on in commercial restaurants.
This has nothing to do with whether or not you approve of prostitution. Prostitution can be legalized by legislation, as it is in most of Nevada. You can always move there, or get enough friends together to change your local law.