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When Basil Fawlty declared "Don't mention the war!" we all got the joke about Britain's ongoing obsession, but it now seems to be a serious diktat in political debate. Beyond Godwin's Law or Ken or Bojo's gaffes, there now seems to be an emerging consensus that anyone who ever mentions Hitler "inappropriately" will be heaped with derision and be greeted with outraged shrieks of "you can't say that". But prescribing any mention of Nazi Germany as 'verboten', whether as historical analogy or factual reference, is bad news for public debate.

The censorious consequences of this 'don't mention' trend are exemplified by those who find Donald Trump so offensive that they immediately reach for the illiberal "ban him" option. JK Rowling is spot on when she says the petition calling for Trump to be barred from visiting the UK, which has hundreds of thousands of signatures, has "crossed a line to stand alongside tyrants". Speaking at PEN America's gala dinner she rightly explains that a vigorous support for free speech, no ifs or buts, has to include defending our opponents as that is what "protects my freedom to call him a bigot".

Don't mention-itis can also mean becoming increasingly tongue-tied, more preoccupied with how we express our thoughts than the substance at hand, and often losing sight of the core debate. How ironic that when Katie Price's son Harvey went on ITV's Loose Women show to talk about vile online abuse about his disability, when he quite reasonably explained that his response to trolls is to say "Hello you c***", the headlines became distracted by his use of a sexist epithet.

More worrying for politics is the way 'don't mention' language policing is given a radical gloss, effectively shushing anyone who doesn't use the correct terminology and worse, prescribing how and what we mention to the narrow tramlines dictated by a new priesthood, usually drawn from representatives of myriad identities or those claiming 'expert' status.

Take today's toxic Gender Wars. A cohort of language vigilantes demand "please don't mention transgender" unless you are given permission and follow the approved line, or can claim legitimate identity cred. If once staid traditionalists warned us to watch our ps and qs, now activists police the world of gender for linguistic correctness. So do not dare use the word transsexual "as a noun rather than as an adjective" (offensive) and only address people using approved non-binary, gender-neutral pronouns and honorifics. Discussion is effectively muted for fear of misgendering, confusing "they", "xe", "mx" or in case you deviate from being anything other than acting as a cheerleader.

If political luminaries such as Germaine Greer and Peter Tatchell or Booker Prize-winning novelist Ian McEwan can be accused of transphobia, what hope for less on-message mortals? So a serious discussion on important questions of gender dysphoria is effectively locked down, with no discussion off-script allowed. Those who may want to critically query the huge spike in numbers of ever younger children seeking gender-identity advice at clinics are told to shut up, or else.

This is not about just one topic: it is part of a trend that tells us "don't mention..." a wide variety of issues – indeed, anything that some self-righteous, self-selected elite commentariat deems out of bounds. This means that an increasing numbers of topics are ring-fenced from critical scrutiny. Rape is one such issue.

This week West Midlands police sacked Pc Richard Mayes for making a 'bad joke' about rape while leading an RAF Cosford training session in the use of tasers. I personally find the use of tasers far more of a contentious issue that the un-PC humour of those training other police officers how to use these lethal weapons effectively. But any mention of rape off message is enough to guarantee a furore. As Mayes notes bitterly: "My life has been ruined by a single word...I said a word that one person in the room didn't like – and it wasn't even that word which got me the sack."

No-one is immune. It may not be so shocking that bad-boy boxer Tyson Fury has been pilloried for his latest 'rape and bestiality will soon be legal' rant. But when everyone from sassy rocker Chrissie Hynde to national treasure Judy Finnigan can be howled down for speaking out of place when talking about rape, you know it's become a taboo topic to mention. When last year Hynde, discussing her own sexual assault, criticised her younger self's recklessness for "getting out of it, hanging out with motorcycle gangs and being lairy", she was hysterically accused of sending out the "wrong message", branded a rape apologist, and with no irony, accused of victim-shaming.

But who elected the feminist cabal that dares to define that right message? Why should they speak for all women? And how on earth can the rest of us discuss difficult issues around sexual violence frankly and honestly if a female rock icon can be hounded for failing to ventriloquise the current, prescriptive orthodoxy?

The latest chilling example of 'Don't-mention-itis' is the accusation of cultural appropriation. The allegation is that the adoption of elements within "minority culture" (such as hairstyles, music, 'fancy dress' or food) by members of a "privileged culture", is deemed an expression of "the power dynamic by which the majority has historically oppressed the minority". This means effectively ghettoising what we mention within our own 'indigenous' culture.

Just last week students at Cambridge University were branded racist for organising an African-themed end-of-year formal dinner. They made the mistake of using Swahili phrases from The Lion King such as "hakuna matata" ("no worries") and a menu featuring Senegal fish balls, Moroccan tagine and Nigerian plantain. Cue howls of outrage, led by Alice Davidson in her contribution, 'Africa Isn't Yours To Appropriate', published on the feminist blog Flygirls of Cambridge. Apparently the dinner may have been approved "if the initiative had come from members of the African Society... who could then determine the menu and terms of cultural exchange."

Does this mean that non-African students should be barred from any courses studying the history or international relations of Africa? It suggests that any mention of Africa per se is problematic. One Medieval Modern Language student (quoted in various newspaper reports on the furore), complained that the problem with the dinner was "it's homogenising an entire continent of over 50 countries", claiming: "The distinction is always made between different European countries".

Please don't mention to said student the constant references to European culture in relation to the EU, presently dominating political debate. And how ironic, when there is concern about Little Englander-style narrowing of relations with the rest of the world, that the cultural-appropriation police, with their premise that only people who are members of a particular culture can express that culture, have set themselves against cosmopolitan cultural fluidity. Please don't mention jazz, the blues or the Mongolian yurts that so many of them are likely to be staying in while glamping at summer music festivals.

The more we allow those that don't parrot the 'right answer' to be denounced as offensive and smeared and the more we're not allowed to mention certain topics, words and concepts, the more monotone political discourse is likely to be. At a time when the world faces unprecedented challenges, restricting ourselves to carefully manicured sound-bites – approved by the "don't mention" censors – deprives us of the richness and complexity of thought and speech that we desperately need to solve contemporary problems. So mention Hitler, Trump, transgender, rape, Africa or whatever as often as you need to, if it helps make your arguments more illuminating, rather than regurgitating sanitised PC dogma.

Claire Fox is the Director of Institute of Ideas. Her new book "I Find That Offensive!" (Biteback, £10) is available now.