Cuba - what a word to conjure with. And what nonsense people have used it to conjure up for half a century now. Those who are determined to see Cuba through the rosy tints of revolutionary spectacles have for decades claimed the country as proof that socialism can work; a Cuban David was able to stand up to the western Goliaths of colonialism and corruption, and Castro’s revolution 50 years ago last week brought peace and plenty - or, if not exactly plenty (given the wicked US blockade), then something better in the shape of brotherly and sisterly content and hospitals far better than those of the National Health Service.

All my adult life this has completely infuriated me. I cannot count the number of friends and acquaintances - at one time almost everyone in the BBC - who have flocked to Cuba and come back with socialist stars in their eyes. It has been extremely irritating to be lectured on Cuba’s moral rebuke to capitalist democracies by people who actually knew nothing about the place - even less, very often, than I did. Cubans are happy, they claimed; it’s a joyful, free society, full of hospitable, joyful people.

There was absolutely no arguing with them; the facts, or rather the absence of facts, simply did not bother them. And that is what is odd. What is the point of admiring something you know very little about?

No doubt there are good things to be said about Cuba. It’s even possible that there are good things to be said about Fidel Castro’s social experiments. But the point is that most people know little about any of it for the simple reason that for half a century it has been hard to discover any truths about Cuba. Almost since the revolution it has been a police state with a high proportion of political prisoners; there has been little or no freedom of expression or association, and people wanting to leave have been severely penalised. That has not stopped many thousands of Cubans trying to get away on little rafts, braving dangerous waters rather than stay with Papa Fidel.

Under such circumstances Cubans have not usually dared to tell visitors much, least of all tourists from the western media. Yet foreign friends of Cuba have willingly allowed themselves to be bamboozled; they have let themselves believe about Cuba whatever either Castro or their own romantic tendencies chose. Most useful idiots share with the rest of us a love of the wonderful Cuban band the Buena Vista Social Club, with its distinctly prerevolutionary Cubansonmusic, from the American film of 1999. Perhaps they are not aware that the band had been silenced nearly 40 years earlier. When, soon after the revolution in 1959, the new government decided to close down cultural and social centres and put countless musicians and artists out of work, the Buena Vista Social Club band was closed down too, until brought back together again in the musicians’ old age - by westerners.

It is a rule of thumb that anyone given to praising Cuba under Castro is a person of poor judgment. This has nothing to do with how much or how little Castro achieved; it has to do with what is necessary for good judgment. An essential part of good judgment is a respect for facts and, in the absence of many facts, a willingness to suspend judgment. It is an intellectual and a moral mistake to become cheerleaders in ignorance. It is the mark of a useful idiot, like those famous western cheerleaders for the communist USSR who were secretly despised by the Soviet leaders.

Useful idiots have always been a mystery to me. When I was an undergraduate in the late 1960s, student radicals would always proudly announce that although socialism might have failed in the USSR - it was never properly tried, they claimed - it worked in the People’s Republic of China. Then I went to live for several years in Hong Kong, off the coast of mainland China, and began to learn a few facts. It wasn’t easy to learn much, as China was a closed and paranoid society, difficult to visit and almost impossible for the Chinese to leave. But I couldn’t help noticing that almost every day bodies were washed up, mauled by sharks, of people who were prepared to brave the shark-infested waters, tied to air beds because they could not swim, in their desperate longing to escape the repression of communist China. This was in the early 1970s in the years following the horrors of the cultural revolution.

None of this stopped useful idiots, such as Jane Fonda and many even more distinguished western commentators, from coming through Hong Kong, on their way to cheerleaders’ tours of China, and announcing that China was a light unto the nations. They were absolutely deaf to any argument, including the knockdown and objective argument that the People’s Republic made it difficult to know any facts. There wasn’t any information.

When I went to China in 1974 we were spied on and saw nothing that was not planned, and this surveillance continued for years. When Mao Tse-tung died in 1976, large numbers of professional western “China-watchers” in Hong Kong admitted privately that they had no idea who Deng Xiaoping (his successor) was. The Chinese government’s statistics - and I edited for a while something called the China Trade Report - were a joke.

Yet these unquantifiable triumphs of Maoist China were solemnly quoted by people who should have known better. China’s economic triumphs were boasted among the bien pensants; they refused to discuss why other cultures in Asia, such as Singapore, Malaysia, South Korea and Thailand, had done much better without communism. And why didn’t the cheerleaders listen to the stories of the hundreds of thousands of people in Hong Kong who had escaped from China? Coming home for holidays I found my former student friends - now in television and academe - deaf to all evidence against Maoism.

Why are people so wilfully credulous? It is one of life’s many mysteries but it’s clearly deeply rooted in human nature. Even Gordon Brown, even now, has his supporters, who still believe in his masterful handling of our economy. Some people seem to need heroes and fantasies so badly that they are prepared to disregard not just the evidence but also the lack of it. My new year’s resolution for myself and for everybody else is to keep asking what the evidence is. And the retort to people who can’t or won’t produce any is: Cuba.

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