Any party that is for self-id is choosing to prioritise feelings over fairness, safety and scientific reason. This means it is very difficult to reason them out of that position, because reason isn’t a basis for choosing it.
That's because it's a faith based position, like a religious belief. If someone believes that a man is a woman just because he says he is, that is based on faith not reason. They seem reluctant to admit that this is a quasi religious belief though, and try to convince us that their beliefs are based on something other than faith.
So we get contradictory claims like the one that women in India need single sex toilets because they are at risk from men otherwise, but women in the UK should be fine with mixed sex. The reasoning is not clear. Perhaps that poster thinks British men are more 'civilised' than their Indian counterparts (which sounds pretty racist), so this is dressed up as women here having more rights than Indian women, therefore single sex anything is unnecessary (which makes no logical sense at all). You can't argue logically for a faith based position.
Anyone choosing faith over science on this issue is going to find it impossible to answer questions with anything that looks like a rational answer. Because ultimately all they have is 'because I believe it is true'. People who believe TWAW should start admitting that this is a belief based on faith, not science. At the moment they just sound idiotic and dishonest.