The question is, are people allowed to have same sex spaces? A place a women can go change clothes without worrying about seeing a penis while she is naked. This seems to me like a rather reasonable desire, and a desire we have indulged for a very long time. I don't buy framing the objection to being naked in the same room as a naked person with a penis as being fundamentally religious. It seems like a basic privacy expectation. In the end, if sex segregated spaces prove to be too thorny an issue for the US to handle, then maybe we should just stop having them. I know I would have killed for private changing rooms when I was in school, and providing them to students doesn't seem like an unreasonable remedy if we can't give them a place that is free of either penises or vaginas.