'no true Scotsman' fallacy.
This is the tack that Nicola Sturgeon took wtih Isla Bryson, and other politicians have repeated, notably Humza Yousaf. 'rapist gender'. 'That individual is a rapist'.
The implication is that a man cannot be both 'trans' and a criminal.
Unfortunately, there's a whole wing of Edinburgh prison that reveals that assertion is incorrect. As well as the well known study into offending rates post 'transition'.
This narrative posits that all men who declare themselves women are 'trans' and therefore 'vulnerable' and 'marginalised' and 'harmless', with the implication that they are incapable of ever doing anything wrong, even going so far as to say that 'There is no evidence that predatory and abusive men have ever had to pretend to be anything else to carry out predatory and abusive behaviour'.
This created a handy loophole of a sacred caste that could not be questioned or suspected. This assertion in itself has probably caused harm, as predators throughout the world noted the opportunity.
The substantial evidence that reveals Shona Robison's stupidity has now meant gender supporters have pivoted to suggesting that any man who is predatory and abusive can therefore not be 'truly trans'.
Women are still not allowed to consider that any man calling himself a woman could be a predator, though. Or note that it's possible to be both vulnerable and a risk/predator.