Literally no one has ever suggested underpants checks at the door.

What is LEGAL and what happens IN PRACTICE are different. Legally, I'm not allowed to swerve around an animal on the road. I still do, and should, but the law exists so that if I cause an accident saying "I saw a bird" isn't a defense.

When it's not LEGAL for any man to be in a woman's bathroom, any hypothetically passing TIM can use it. And be actually safer because there are no "cis men" getting in. Women do not, in practice, stop butch looking women and demand to see their genitals. We don't question anyone because the chance that we're wrong would be humiliating to all parties. But when a TIM or 'cis male' is creeping women out we're able to get them removed because the law is clear about which side it's on. The law exists so that a creep can't use "i feel like a girl today" as a defense.

When it is made legal for any man to use the women's bathrooms, there is no way to remove a creep. There could be 10 men in there making sexual threats to you, and you can't make them leave or even report it. You're the bigot if you do. You can't prove what they said or did, you can't prove 'creepy'. The law's stance is "get raped first, then i might care. IF you can prove it." Literally every rapist and pedophile is allowed in women's bathrooms. Allowed to hang out in there all day long if they like, until AFTER they've been proven to have committed a crime. And once they get out of prison they can use them again. In practice the result is that all vulnerable women are excluded form all public bathrooms and therefore have limited access to public spaces.

The next town over from me houses a protection prison, i.e. lots of pedophiles get released from there and walk straight into the community. Ask that woman next time, how many of them she thinks should be able to hang out in the women's public toilets without being questioned?