I agree with you as far as your post goes, Richard, but it doesn't go quite far enough. What about people who are biologically "intersex," their bodies are somewhere in between?  According to the Intersex Society of America, that's  about 1 percent of us. http://www.isna.org/faq/frequency.  

It makes sense to me to just include "genderless" private stalls for anyone who wants total privacy.  And that includes anyone who wants to avoid the possibility of having to share a restroom with someone who thinks their gender is other than what it was at birth. Small businesses that already have genderless/family restrooms are already ahead of the game. Public locker rooms and showers are a whole different scenarios.