What made me SMH was someone high in politics (I didn't catch who, or I might even be tempted to officially ask them about this) say that, by having all trans-women have to use male facilities, it would make "everyone safer".
Clearly not the trans-woman.
I'm sympathetic to women who don't want "I identify as a woman, please ignore my appearance, physique and attitude" individuals 'self-identifying' when challenged why they're wandering into the women's changing rooms (and the issues of actual rapists who are dangers to the prison-population subset they find themselves in[1]). But, for anyone on the other end of the continuum, all the way up to being surgically female in all ways (and who may well pass without comment, and certainly live and work as a woman in all other respects), they are now those forced to gamble against officialdom finding out, if they'd rather not use the male facilities[2].
An all-or-nothing approach is clearly wrong, either way. The worst fears of cis-women may be valid in the cases of some cases of 'trans-women', but forcing AGAB-alignment is more bad news for genuine trans-women. Hard cases make hard laws, as they say. This isn't an issue that should ever involve me, but I'm probably feeling more dissappointed in Kier's stance on this issue[3] than even those things do more directly do so. (Is now the time to invoke the "my dad knew your dad" line and try to contact him..?) My reading of the SC decision is that the interpretation of the current laws has to be made in this particular direction (whether or not ably assisted by underlying transphobia), but perhaps this more means that the applicable text used needs refining to allow the proper measure of subtlety and balance.
Even if everyone obeys the 'new' rules (at least those not already with mischief on their mind), it's been shown that "gender bouncers" stationed outside women's restrooms in the US tend to stop and question a whole lot of 'butch-looking' AFABs in their quest to try to stop the few actually-trans individuals out there. (Who may well be deliberately far more femme, which then naturally should mean that very girly-girls ought to be challenged at least as much[4], which I'm sure won't help matters!)
And I can just imagine the kerfuffle when a trans-man, in diligantly obeying this new stricture (presuming nobody's specifically made the 'exception' for them, by clearly posting the site's own policies on their status), strides into the female facilities.
As a man, I know I'm not the best person to pontificate on this. My best credentials are that I've known a handful of trans-women (that I know of), in my time; only one of which I know had undertaken 'the full monty' surgery, but I know that only because I was one of those trusted to be aware of his>her taking time out for various stages of the process. Perhaps I'm coloured in my opinion by none of them (even the ones who 'don't really pass') being any danger to women, all would have been in far more danger from bigoted men (or, indeed, bigoted women). The couple of 'sporty' ones were also never going to be a competitive problem in women's sport (at best, from tail-end in the men's competitions to 'also-ran' in the women's); at least one gave up on sport entirely, in fact, but at least partly from prejudice from the men. As to the cis-female perspective, I can only report that I'm aware of no woman who felt particularly threatened (physically or sportingly) by these; no doubt there'd be those not in the same circles who have felt trepidation at the prospect of interactions, but I never got any such vibes from anyone already acquainted with those concerned (not that I'd be privy to all the gory details of feminine gossip, of course).
I have, however, known cis-men and cis-women who have been troubled and troublesome individuals in ways that cause far more disturbance to society and my own social groups. Even if you try to reapportion it to the relative numbers of cis/trans out there, I can't really see the social panic as justified, just yet again an example of prejudices punching-down on minorities for (non-mythical, sure, but still mostly outlying) percieved ills.
[1] There must already be plenty of experience with male-on-male and female-on-female (cis) rapists having to be segregated, supervised, etc, in their undoubted half of the prison estate. And plenty of reasons why those imprisoned for non-sexual offences might need monitoring for either vulnerability or as the source of trouble. Being trans just adds more factors to consider in both keeping them safe and keeping others safe from them, but would hardly be an unprecedented level of measures to have to take on particular cases.
[2] Essentially self-outing themselves, and exposing them to possible dangers (violence, if not sexual violence) within.
[3] I can understand the pressures he's under on this, but don't agree with them. On other things, recently, I understand the needs and reluctantly agree with how he's dealt with them (while looking for alternatives).
[4] Drawing from my favourite author, there's the scene in Monstrous Regiment where the soldiers/'washerwomen' are inflitrating the fortress and immediately get 'caught' in their 'deception'. "Daphne", however... Yes, it's fiction, and effectively played for laughs, but it's still a good allegory for what can happen.