Just got this on FB, it sums up it pretty well.
If you're going to separate the sex organs, then be consistent about it. I doubt sex attacks would really be a problem, but it isn't in dual loos, either, it's just the little things (over this overpopularised small issue. I looked it up, several American states (though not North Carolina) don't even allow you to officially/legally change your gender.). It's that privacy and small comfort of own sex. Either make loos just for both sexes, either do it by sex organ, not gender brain.