Firstly, trans women aren’t the threat, men are. Men are potential threats regardless of any other characteristic they have, including gender identity. That is why all men need to be kept out. If you haven’t understood that our argument is about the threat men present, you haven’t understood our position at all.
Secondly, this issue matters so much as at its heart it is about whether or not our society regards women and girls as being entitled to the most basic human rights. If women can be locked up with men, required to share bedrooms and sleeping space with men, required to get undressed in front of men ( as the young women on the beauty course with the rapist Isla were), required to discuss sexual trauma in front of men, and even more than that, are shamed and ostracized if they refuse, then women and girls are not regarded as being entitled to the most basic human rights and dignity. And if we aren’t seen as worthy of that, we can never be equal or advance our rights in society.
This debate is essentially one over the worth, and level of humanity, that women and girls are seen as having in society. That is why it is so crucial.