By debating whether they are women or not is essentially asking are they valid as women. It’s debating their existence because if they say they really are women and you say they are not, you’re basically saying that what they say they are, doesn’t actually exist.
I can help you with the debating bit. Transwomen are not women; trans men are not men.
I’d also argue that if you perceive your entire existence hinges on the validation of a chosen identity by outsiders, then you certainly have a mental illness. The capacity for self-validation and a coherent sense of self driven by self-awareness is an important component of being an adult human.
It is one of the great tragedies of being a woman that our socialisation into femininity teaches us to seek constant external validation. It is neither healthy nor useful to us, particularly as we age. Men aping the worst and most damaging aspects of female socialisation is not an indicator of mental well-being.
I believe transwomen, (and men exist). What I don’t believe is the explanation of their chosen “identity”.
Do I believe there are men who desire to present as womem, or women who wish to present as men? Of course. You can’t turn around lately without falling over the adherents of that narrative.
Do I believe they are literally of the other sex, physically or mentally? No. Never.
Does that make them stop existing? Certainly not. Even in the ontological fog which seems to permeate the trans narrative, material reality is still in operation.
I have no interest in marginalising transpeople, denying them any of the rights and benefits which accrue to humans in society. I want them to access the kind of physical and mental healthcare which will prevent or cure the surgical and drug-induced mutilation of their normal, healthy bodies.
I do not believe that while I wrote this, a single transperson winked out of existence.