On Tuesday, tourists visiting the Houses of Parliament at Westminster found demonstrators outside, chanting and waving placards. Nothing unusual about that, of course, but this demonstration was different.

First, they weren’t chanting slogans, but singing hymns. The placards quoted the prophet Isaiah: “Woe unto them that decree unrighteous decrees.” But no, they weren’t protesting against abortion, or stem cell research, or any of the usual moral issues that unite people of faith. In fact, many of them weren’t religious at all. The demonstration brought together the strangest bedfellows: some of Britain’s funniest comedians, led by Rowan Atkinson (“Mr. Bean”), alongside the Reverend Ian Paisley, who thinks TV is the Devil’s own work, plus just about everybody in between: Jews and Christians, Protestants and Catholics, believers and atheists, the coolest of the cool and the most defiant of the uncool.

Even more surprising, they were united in opposition to a measure that is supposed to protect religion: the Racial and Religious Hatred Bill. It was intended to ban abusive, insulting or threatening words that either intentionally or recklessly incite hatred of a religious community, thereby placing religion on the same legal basis as race.

But the biggest surprise of all was that the protesters won. For only the second time since Tony Blair became prime minister nine years ago, the government lost two divisions in the House of Commons. Most embarrassing of all, one was lost by only one vote – Mr. Blair’s. The prime minister had been told to go home by party managers, confident that they did not need him. There was nothing for it but to admit defeat, and so the bill will become law with two crucial amendments that will probably render it a dead letter.

The trouble with this bill is that just about everybody is against it except Muslims. And thereby hangs a tale. The bill has its origins in the most notorious episode of Islamic censorship: Salman Rushdie’s novel “The Satanic Verses.” It is the fruit of many years’ lobbying by the Muslim Council of Britain, which emerged from the Rushdie affair. The British government yielded to this lobbying about two years ago, in response to the threat of Islamist terrorism and the power of the British Muslim community. It was a Faustian pact. The government in effect said to Muslims: Stay loyal to us and we will enshrine protection for Islam in law.

Muslim leaders accepted the deal, but at the last election the Muslim vote deserted the Labor Party anyway, over Iraq and the war on terror. The government’s majority in the House of Commons was halved to about 60. That should still be enough, but last fall Mr. Blair suffered his first defeat on an anti-terrorist Bill brought in after the London bombings. A growing band of leftist rebels defies him on every issue, in the hope of hastening his promised departure from Downing Street. The House of Lords, where the government has no majority, seizes every chance to rewrite legislation. Though the Lords can be overruled, sometimes their amendments attract widespread support in the House of Commons too. And so it proved this week.

The Religious Hatred Bill was always going to be a golden opportunity to humiliate the prime minister, because the case for it was weak and the government’s motives were suspect. The House of Lords, which includes judges and bishops, sent it back to the Commons with two main amendments. They took out the clause that would have made it an offense not only to use “threatening” but also “abusive or insulting” words about a religious group, and they insisted that a person must intend to incite religious hatred, not merely do so “recklessly.”

It is already an offense to threaten people, and it is notoriously difficult to prove intention. So these were “wrecking” amendments, designed to stop the new law restricting freedom of speech. The government demanded that they should be reversed when the bill came back to the House of Commons for the third and last time this week. But it relied too heavily on the trump card of party loyalty, and failed to realize that many of its own legislators agreed with the motley crowd of protestors outside.

Journalists, too, are worried that legitimate criticisms of Islam – about its attitude to non-Muslims or to women, say – might fall foul of the new law. They are incensed that the British government is giving legal sanctions to Muslim organizations, which, in the absence of state censorship, seek to intimidate writers into practicing self-censorship.

The case of the Danish newspaper Jyllands-Posten, which printed satirical cartoons depicting the Prophet Muhammad, has sent shock waves through the European press. Danes have been threatened and boycotted throughout the Muslim world, the Saudi and Libyan ambassadors have been withdrawn from Copenhagen, and journalists suffer daily death threats and bomb scares.

In fact, Muslims would benefit from criticism and satire more than most. That was certainly the view of Zaki Badawi, the eminent scholar who believed that Islam could adapt to Western culture without losing its identity and founded the Muslim College in London to train imams to adopt the English language and culture. Though born in Egypt, Dr. Badawi understood that the British, having created the world’s first free press, would not view kindly a minority that demanded its suppression in the name of Islam. Zaki Badawi died last week, depriving British Muslims of a voice of sanity.

I can only hope that Mr. Blair will draw the right conclusion from this failure: that it is always and everywhere wrong to appease Islam’s totalitarian tendency. While the prime minister was doubtless regretting his Faustian bargain with the, President Bush was delivering his State of the Union address, in which he sent a much clearer signal to the Islamists: “We love our freedom, and we will fight to keep it.”

Mr. Blair has often voiced the same sentiments. As the world slides towards military confrontation with Iran, he needs to reiterate that message. For the threat of Islamic intolerance unites left and right, liberal and conservative, people of all faiths and none. If only Mr. Blair had looked out of his window at the demonstration in Parliament Square, he would surely have realized that the people protesting his Religious Hatred Bill were all his natural allies.