I may or may not be addressing all your points in your statement, but here is what I think from what I've read of your opinion.
Your argument centers around the faulty idea of essentially "If it doesn't cause others physical harm, then it is okay and shouldn't be regulated." And the idea that, "There is no survival or evolutionary advantage..." to having laws or societies forbidding contact between the sexes while taking a shit or piss.
It causes harm to societal order. That in itself is cause for regulation and is a much higher priority in most people's minds than you may believe.
This is not the point of these kinds of legislation like that of North Carolina and more recently Mississippi. These laws are not designed to give separated bathrooms any sort of survival or evolutionary advantage. The point is to ensure a current societal order and that *the majority* are comfortable in these restrooms and preventing harassment between the sexes while sexual genitalia are exposed to perform these functions.
The issue the law is addressing is preventing abuse for a biologically female person entering into a male restroom being subject to harassment or worse and vice versa with a biological male attempting to enter a female restroom.
Whether the American political left wishes to like it or not, the LGBT are still a *small* but very vocal minority in the world overall. In a Democratic Republic, such as the one in the USA, the majority rules, not the minority. It happens every election cycle. And as of right now, there are more people wanting to vote in a politically right-sided candidate vs. one of the left.
The Left's ideals are not morally perfect, neither are the Right's. A lot of people don't like to think they're wrong, but in this case, the Right has a point in keeping this law, even though the Left seems to be arguing a "slippery slope" fallacy whereas somehow all LGBT rights disappear if this law is upheld in a Federal Appeals court or Supreme Court.
For half this country, America symbolizes liberty. For another half, this country symbolizes equality. The two philosophies used to coexist, but recently it seems that is no longer the case.