It's such an imbecilic attempt at a 'gotcha'. No one has an open-door policy whereby any random member of society is able to use their toilet, and your home toilet is a single-person room that locks from the inside.
I've been spied on by a man over the top of a cubicle in a publicly accessible toilet. Amazingly, this has never happened to me in my own home.
Yeah, I mean in general TRAs have the worst gotchas. And the weird thing is, they clearly think they're doing something smart. My favourite low-IQ clapbacks, ranked in order of amusing stupidity, are:
1. You have a unisex toilet in your house!
2. Transwomen are just like Black women, for reasons!
3. Urgh, why are you so obsessed with other people's genitals?
4. We just want to pee!
5. Trans are a tiny and highly vulnerable minority. Why are you getting so angry about less than 1% of the population? Don't you have anything better to do?
All of the above are based on either deliberate or unknowing semantic category error/ontological error and I do find it baffling that TRAs, who often like to pretend to some mysterious higher state of insight, don't seem able to recognise what a 14 year old of average intelligence should be able to point to with ease.