Earlier quoted context omitted.
What I haven't seen discussed is the real objection going on is that NC insists you use the bathroom as defined by your birth certificate, and you can change that post-op. So people think that's too onerous, so what _should_ the standard be? Should you simply file something stating you are whatever gender? Do you have to present as the gender to some degree? Who decides if you are doing it enough? Etc.
The problem with that approach is that not all transgender people elect to have operations, so making that the minimum bar is unreasonable. A much more reasonable (non-fear mongering) approach is to use the gender the person identifies with. I don't know how you set that bar, maybe it's obvious, maybe it requires a note from a physician or similar. I think it would be fairly obvious to discern someone who's actually…
The problem with /that/ would be that non-transgenders would possibly feel uncomfortable with that - which I believe, but correct me if I'm wrong, is why there's gender-segregated bathrooms in the first place.
The only solution would be, as the other commenter says, to only have unisex bathrooms and to tell anyone that complains about that to fuck off.