I would not go into a woman's restroom if I were a man, ever. But I would expect that restroom facilities would be provided that allowed me to keep my daughter safe - your daughter would be safe from sexual predators if biological males were banned from the ladies' restroom.
As for kid-knapping, well, that's something that I haven't thought about.
But it makes sense to me that fathers make sure they can accompany their sons in the gents' and mothers do likewise with their daughters.