It has become a secular form of blasphemy to question the rights of transgender people to identify with whatever sex they choose. So when Jenni Murray, the presenter of BBC Radio 4's Woman's Hour, came out and said the unsayable - that trans women, born as males, are not real women - she knew the outrage would be mighty, and the calls for punishment swift.
In an interview with the Sunday Times, Murray acknowledged that she was entering “the most controversial and, at times, vicious, vulgar and threatening debate of our day”. She is not transphobic or anti-trans, she said, but she refuses to accept that “an individual born into the male sex, socialised into the expectations of the masculine gender, can simply decide to take hormones and maybe have surgery and ‘become a woman’”. Without having had the lived experience of growing up female, and struggling to escape the social strictures still imposed on women, trans women may end up reinforcing stereotypical notions of femininity: “a man’s idea of what a woman should be”.
Sure enough, Murray was instantly condemned as a bigot and a bile-spouting dinosaur, social media went into a frenzy, and the obligatory petition calling for her to be sacked from Woman's Hour was begun. A more measured response came from Rachel Cohen of Stonewall, the LGBT rights charity. "Whether you are trans or not, your identity is yours alone," Cohen wrote in an open letter. "Trans women have every right to have their identity and experiences respected too. They are women - just like you and me - and their sense of their gender is as ingrained in their identity as yours or mine".
The BBC subsequently issued Murray with a warning, saying it had “reminded her that presenters should remain impartial on controversial topics covered by their BBC programmes”. Whether this will be sufficient to satisfy Murray’s opponents remains to be seen.
It is worth remembering that Murray's belief in the illegitimacy of trans women's claims to be truly female was once commonplace among feminists. If people thought that what Murray said was brutally hurtful "hate speech", they should probably stay away from the chapter entitled Pantomime Dames in Germaine Greer's book, The Whole Woman. In it, Greer describes sex-change surgery as "mutilation", likens trans women who insist on occupying female-only spaces to rapists, and condemns the "spurious femaleness" of "a man [WHO]decides to spend his whole life impersonating his mother (like Norman Bates in Psycho)".
There is no justification for Greer's hostile invective. But the conundrum that Murray raises - what is a woman? - is philosophically interesting, as well as ultimately unanswerable. If we define womanhood in basic biological terms, by chromosome count, say, or by the potential ability to give birth, then trans women are ruled out immediately. If personal identity is merely a matter of choice or deep inner conviction, however, then it's all up for grabs. By extension, the notorious "black" US activist, Rachel Dolezal, who actually turned out to be white, would be justified in maintaining her much-cherished black identity while claiming - as she did - that "white isn't a race, it's a state of mind." It all depends how far you're prepared to go with that logic.
I think that most people would acknowledge that a trans woman is not female in the same way that natural-born women are female. There is a difference. But there’s no need to turn it into a battle of ownership, or a competition over which of us is the more “really real”.
Of far greater concern is the authoritarian impulse to shut down unpopular or unfashionable views, often carried out - ironically enough - in the name of tolerance. This has become a particular problem around transgender issues. Anyone who does not conform to the orthodoxy is routinely excoriated, frequently accused of inciting violence against trans people, and sometimes even threatened themselves. Germaine Greer joins a growing list of veteran feminists who are unwelcome at many universities because their beliefs are now considered toxic and dangerous. Greer remains characteristically unrepentant, insisting that she could ask a doctor to give her long ears and liver spots but it wouldn't make her a cocker spaniel.
This is not a debate about who gets to call themselves an authentic woman. The row over Jenni Murray’s remarks is merely the latest bout in the ongoing struggle over which opinions are considered sayable and which will be silenced. The mistake is to engage in this fight in the first place. If we call ourselves tolerant, then all must be heard.
Fionola Meredith is ajournalist and commentator