Can you post more of your ethical debates? While quite gross, it's really interesting.
I agree with you, the toilet's position is weakened by his inability to accurately determine his clients' menstrual situation. I'd also question whether he's being selective in his application of Jewish law - surely other aspects of being a human toilet are forbidden?
But do these weaknesses in his argument undermine his stance from an ethical perspective? In this case he does know she's menstruating and let's assume everything else he's doing is fine (?!?).
In which case the debate comes back to what constitutes discrimination against women. Only women menstruate, which means it's obviously a male/female issue. But that doesn't mean by extension all things female are discrimination fodder.
Does a woman have an equal right to piss on a human toilet as a man? I would have thought this fell into the area of consenting sexual relations NOT basic rights - he has a right to say no for whatever reason he likes. Saying he must let anyone piss on him implies he is an inanimate toilet, which gets into sex slavery etc. Which is ethically wrong, due to coercion in an area that is fundamental to self-expression.
I agree with the toilet I think.
(not something I ever thought I'd write!)