There are, in the annals of cinema, few scenes more likely to have men of a certain age sobbing into their handkerchiefs than that wonderful moment in Zulu. You know the one I mean.

Alone and exhausted at Rorke’s Drift, the massively outnumbered British defenders hear the Zulus singing their haunting war chant.

‘Do you think the Welsh can’t do better than that, Owen?’ murmurs Lieutenant Chard (played by Stanley Baker).

There are, in the annals of cinema, few scenes more likely to have men of a certain age sobbing into their handkerchiefs than that wonderful moment in Zulu featuring Stanley Baker

‘Well, they’ve got a very good bass section, mind, but no top tenors, that’s for sure,’ replies Pte Owen (Ivor Emmanuel).

Then, his voice unexpectedly resonant in the morning air, Owen strikes up ‘Men Of Harlech’, and then — well, you probably know the rest.

And if you don’t, you should watch the film without delay.

Even today, 54 years after its release, Zulu has lost none of its power. It is a film about men under fire, of course. But it is also a film about heroism, fear and sacrifice.

Set during the Zulu War of 1879, it is a patriotic film, but not a jingoistic one. When the Zulus sing one last song to honour the courage of the British defenders, or when Lt Chard gazes wearily over the piles of African dead, there is rarely a dry eye in the house.

Even today, 54 years after its release, Zulu has lost none of its power. It is a film about men under fire, of course. But it is also a film about heroism, fear and sacrifice

So when the Silver Screen Cinema in Folkestone announced a special screening of Zulu to raise money for the Armed Forces charity SSAFA, they could hardly have made a better choice. Or so you might have thought.

But some people see things differently. Almost unbelievably, this week it emerged that more than two dozen signed an open letter to the town’s mayor, urging him to cancel the screening.

Their explanation is, in its way, a masterpiece of ignorance. ‘We believe,’ they write, ‘that the choice of the film Zulu, with its inaccurate portrayal of historical events and its distortions and racist overtones could have a negative effect on relationships within the changing and richly diverse communities here in Folkestone.’ Where do you start with all this? Is Zulu markedly less accurate than other films (not least Hollywood’s recent versions of history, such as Saving Private Ryan, which ignored British and Russian involvement in World War II)?

Not at all.

Is it demonstrably racist? Again, obviously not. The film takes care to show the Zulus as noble adversaries.

Little House on the Prairie, pictured, is facing a boycott because of the author of the original books for 'anti-Native and anti-Black sentiments'

Indeed, the current Zulu leader Mangosuthu Buthelezi served as an adviser to the filmmakers and actually plays his own great-grandfather, King Cetshwayo.

Could a charity screening of Zulu really have a ‘negative effect’ on race relations on the Kentish coast? Is it plausible that, having seen it, people will start throwing spears at each other, or barricade themselves in their homes and open fire on passing foreigners?

Of course not.

If this story were just a bizarre anomaly, it would be easy to laugh it off. Unfortunately, though, it is part of a trend.

For there was another story about censorship this week, this time from America. Yielding to pressure from more self-proclaimed activists, the U.S. Association for Library Service to Children has removed Laura Ingalls Wilder’s name from its award for children’s literature.

As many readers will know, Wilder was the author of the Little House On The Prairie series, published in the Thirties and Forties, which told the story of a pioneer family in the 19th-century American West.

Turned into a hugely popular TV series in the Seventies and Eighties, the books are the embodiment of old-fashioned, innocent children’s entertainment, which makes them irresistible to little girls, even today.

So why on earth take Wilder’s name off the award? You can probably guess. Wilder’s books, her critics claim, are full of ‘anti-Native and anti-Black sentiments’. The characters say things like: ‘The only good Indian is a dead Indian.’ Worse, they even call black people ‘darkies’.

Today, we rightly regard such terms as utterly unacceptable, but the fact is that in the 19th century, when the stories are set, people really did say such things — and worse.

Never mind that Wilder was a product of her time, as are we all. For when the activists shouted ‘Racist!’, not even the childlike innocence of her stories was enough to save her.

I am not alone, I know, in feeling nothing but contempt for the disingenuousness, mean-spiritedness, sanctimony and intolerance of these people. I’m not alone, either, in feeling utterly infuriated by the cowardice of the authorities, who are incapable of realising that appeasement only encourages them to find a fresh target.

Films such as Saving Private Ryan ignored the British and Russian efforts of WWII

What I find really depressing, though, is that this is becoming such a familiar story. The activists make a fuss. The rest of us scoff, sigh or shrug them off as maniacs.

But the authorities, terrified of being branded racist, give ground. And so, almost without anybody noticing, we take one more step towards a culture defined by the suffocating narrow-mindedness of the lunatic fringe.

If that sounds too sensationalist, then consider this. Only a few months ago, a friend at Oxford told me that she no longer teaches Joseph Conrad’s novella The Nigger Of The ‘Narcissus’, because the title alone means she risks being branded a racist.

Never mind that Conrad is a novelist of genius and that Narcissus is a book of note. And never mind that the whole point of reading fiction is to take us outside our bubbles, to challenge our preconceptions, to surprise and provoke us.

Again, of course, it would be outrageous to use such terms about black people now, but surely students are capable of understanding the difference between moral values in the past and moral values today?

The irony is the ultra-liberal censors, these new fascists of our age, preach about diversity. But they are obsessed by only one thing: race, or, more accurately, accusing others of being racist. They’re certainly not interested in diversity of thought, which might challenge their petty ideological prejudices.

So Zulu is out. Little House On The Prairie is out, too. What next?

An obvious target is anything written by a ‘dead white man’, to use the liberal fascists’ own jargon. William Shakespeare is out, obviously, because of the anti-Semitic figure of Shylock, the moneylender in The Merchant Of Venice, and the alleged racism of his portrayal of Othello (the ‘thick-lips’, as one character calls him).

Who else? Dickens has to go, partly because of the anti-Semitic caricature of Fagin in Oliver Twist, but also because his women are all drippy, passive fantasy figures.

Rudyard Kipling is definitely out, because his books show the British Empire in India in a good light.

How long before the censors come for Agatha Christie, whose early books also stereo-typed Jewish people and who was also guilty of using the ‘N’ word in the title of one?

And amid the current hysteria about sexual harassment, will any cinema ever be allowed to show an old 007 film?

Where will it end? Well, it will never end. And because these censors have no sense of humility, they cannot conceive that people in the future will doubtless find us guilty of prejudices invisible to us today.

By then, though, what will be left of Western culture? For if Zulu isn’t safe, if Laura Ingalls Wilder is not safe, if even the slightest hint of political incorrectness is enough to disqualify you, then nothing and nobody is safe.

The truth is that these people are the enemies, not just of tradition or even of tolerance, but of the imagination itself.

They talk endlessly about celebrating difference. But what they want to do is to suppress difference, control the imagination and rewrite history. And that, of course, is why they must be fought.