Why can't transwomen use male toilets?
Some men dress as women for sexual reasons, which is fine - but there is a time and place for that, and it's not in the public arena.
Others feel as though they should have been women, which is a shame, but life doesn't always give us what we want, and it is unreasonable to expect the rest of society to collude in their fantasies when doing so poses a threat to women - even if that threat is not from the transwomen themselves. If transwomen want to dress and act in a way that they see as 'female', that's fair enough, but it won't alter their biological reality, which is that they are male, and because of that reality they should, IMO, use the Gents. With the other men. When they leave they can go back to the behaviour they perceive as 'female' and expect others to go along with it, as it harms nobody and puts nobody at risk.
Having men in the Ladies is a risk, even though not all men are a threat. It is the inability of anyone to know which men pose a threat and which don't (whatever they are wearing) which is the issue, and if one man is able to use the Ladies with impunity, there is no way to stop the others.
What is so complicated about that? And why shouldn't biological males use the male facilities?