That is the point of single sex spaces. Any male entering them is willfully disregarding women's consent and can be immediately kicked out. This strict crystal clear standard makes it relatively easy to prosecute offenders.

By stepping into that space he has violated women's consent and is committing at bare minimum Voyeurism. It doesn't matter if he is leering or not. The women there did not consent to any male viewing their naked bodies. He could be a world famous painter who just wants to paint naked women, but if they did not consent to it he is to all intents and purposes a sexual predator and his neutral artistic intent is irrelevant. There's a reason artists hire models and don't go traipsing into opposite sex changing rooms when they need to practice drawing the human form. Consent matters.

If we make exceptions for some males we can no longer hold predatory voyeuristic & exhibitionistic men accountable which was why the Wi Spa fiasco happened. What if the man who entered the women's area was one of those extra super special exceptions? What if he really felt deep down that he was actually a woman on the inside? We see exactly how that plays out in the real world. Women are told to suck it up and now they no longer have a safe place to change nor are they allowed to seek justice for Voyeurism and Indecent Exposure. The comfort & desires of 1 male has been put above every single woman who goes to that spa.

Less than 1% of rapes result in convictions

Now if the conviction rate for rapists is 1% how low do you think it is for voyeurs and exhibitionists? I bet a lot of them face 0 consequences for sexually harassing women. Sexual harassment & assault is notoriously hard to prove and convict (especially in places where for privacy reasons cameras are not allowed like you know a locker rooms/spa rooms & don't get me started on the predators who place cameras in women's restrooms/locker rooms so they can violate women even further by posting the footage online. About 80% of the victims of spy camera porn are women.).

Women's only spaces are one of the very few areas where holding sexual predators accountable is a no brainer. If he wasn't a sexual predator he wouldn't have entered the women's only area in the first place. By making exceptions for men who claim to be women we go back to square 1 with that lovely 1% conviction rate. Allowing any male in destroys the entire purpose of women's single sex spaces. At that point we may as well make all spaces unisex, which leaves women once again having to deal with sexual harassment/rape with no recourse or justice the vast majority of the time making the space safe for no one. Now that's what I call a lose lose scenario.