They'll just title themselves as a "private club", like other organizations that wanted to continue discriminating after public accommodations were enacted.
And in all fairness, FB originally started that way when you needed a university email address to join.
As long as we are updating the definition of public accommodation, we can also define the "private".
My point was more that it is not unreasonable to look to regulations to deal with Facebook. The regulations do not necessarily have to be "public accommodations", I just cited them as the most relevant legal concept I was aware of.
I am more than happy to give Facebook as much rope as it needs.
No worries though, other sovereign entities are trying to do what you suggest, so we get the best of both worlds. It's a wonderful demonstration of why nation-states should defend their independence.
And in all fairness, FB originally started that way when you needed a university email address to join.