If Anonymous has his or her way, hundreds of demonstrators will launch 'the London Scientology Raid' on the 'church's' British HQ this morning. He or she is promising an 'EPIC to show that we actually give a damn' and whoever he or she is, the British Anonymous isn't alone.

Anonymouses around the world are using Facebook and chatrooms to co-ordinate protests and cyber-attacks on Scientology websites. They say they won't give their names because they want 'to show that we are everyone and everywhere', but I suspect fear of the Scientologists' expensive lawyers is an equally powerful argument for discretion.

Anonymous says the sect provoked the assault by seeking to suppress a video of Tom Cruise attacking psychiatrists and doctors for their failure to stop drug addiction and crime. To Cruise and his co-believers, medics are idiots who can't supply effective treatments because they don't understand that humans are haunted by the souls of mentally ill aliens dumped in volcanoes off Hawaii by Xenu, the evil ruler of the Galactic Confederacy 75 million years ago. (I'll spare you the rest.)

It is not Mr Cruise's most polished performance. He's occasionally incoherent and at one point emits an unhinged laugh. Scientologists claimed they owned the copyright to the film that had been edited to make Cruise look silly and demanded YouTube remove it. As soon as they did, Anonymous posted it back.

Outsiders may wonder why they care so much about one sect. The supernatural stories of all religions are ridiculous to those who don't believe them and Scientology only sounds more sinister than most because it is a modern invention. True, there are well-sourced accounts of Scientologists persuading converts to part with large sums of money, but all religions can lighten the pockets of the faithful.

All in all, Rowan Williams seems a more deserving target for mass protests this weekend. Say what you will about Scientologists, but at least they haven't come out against the emancipation of women and equality before the law.

They have, however, exploited a trend as dangerous as the retreat from liberal values in the face of the threat of Islamism. They have learnt that rich organisations and rich men can use British courts to suppress the freedom democratic societies rely on, both here and abroad.

The pay-off line to a 2005 episode of South Park said it all. The show was a satire on Scientology in which a cartoon Cruise was exposed to near-continuous ridicule. In the final scene, he cries: 'I'm going to sue you... in England!'

The real Cruise can't sue the makers in the US, where freedom of speech is protected but, like his cartoon counterpart, he could be confident our judges would gladly shelter him under our authoritarian libel laws if he found an excuse to come here. The same thought struck TV executives and the Scientology episode of South Park has never been shown by a British station. Even though you can see it on the web, lawyers would turn pale if I suggested repeating South Park's running gag at Cruise's expense in a British paper.

South Park wasn't a one-off. Andrew Morton, chronicler of the Windsor-Spencer divorce, has just produced a biography of Cruise which says much about his relationship with his strange church. Not only can you not buy a copy here, you can't order one from abroad. Try to buy a copy online and the US Amazon site will tell you that 'the publisher has authorised the distribution of this book only to customers within the United States and Canada'.

The Economist has all but accused St Martin's Press of cowardice, but I think its editors know about the key modern censorship case of Sheikh Khalid bin Mahfouz v Rachel Ehrenfeld.

For several years now, bin Mahfouz, a billionaire Saudi banker, has used the English libel courts to punish a succession of newspapers and publishers. In 2004, Mr Justice Eady ordered Rachel Ehrenfeld, a New York-based academic, to pay him $225,000 in damages and costs and destroy all copies of her book. The novelty lay in the fact that Dr Ehrenfeld wasn't a British citizen, but an American. Her book hadn't been printed in Britain or publicised in Britain. She offered no defence because she didn't think Eady had the power to tell an American what she could and couldn't write.

More extraordinarily, bin Mahfouz wasn't a British citizen either. He has adopted Irish nationality and agreed to pay New York authorities $225m in return for the dropping of charges about his role in the collapse of the fantastically crooked Bank of Credit and Commerce International.

Despite this, Eady ruled that bin Mahfouz had a reputation worth protecting in England. He then decided the sheikh could sue Ehrenfeld because a few copies of her book had slipped into the country via Amazon. The net, which was meant to encourage openness, became the excuse for a pulping order.

Publishers and every variety of American journalist from left winger to neo-con are demanding court judgments and new laws from US politicians to protect them from Eady and his kind. They have grasped that, far from promoting freedom, the net is allowing Saudi billionaires, Scientologists and soon, I imagine, Vladimir Putin's stooges and the agents of sovereign wealth funds to come to London and secure a banning order that could be enforced anywhere in the world.

Today's anti-Scientology protesters may seem obsessive. Although they promise to be non-violent, their planned raids could turn nasty. But they understand better than bowdlerising judges and appeasing archbishops that the freedom to speak, argue, examine and satirise is the best defence against all the cults that seek to indoctrinate and subjugate our fellow citizens.

· This article was amended on Tuesday February 12 2008. We mentioned a censorship case that featured Ruth Ehrenfeld when we mean to say Rachel Ehrenfeld. This has been corrected.