[Joseph Loconte is a senior fellow at the Ethics and Public Policy Center and the host of the weekly television/Internet program "Britain and America."]

The chill wind and cheerless skies didn't discourage thousands of Londoners from trudging to the Queen Elizabeth II conference center on Saturday, January 20, to hear a debate about "the clash of civilizations"--the challenge of militant Islam to the West. The overflow event, sponsored by the city of London, pitted American Middle East scholar Daniel Pipes against the leftist mayor, Ken Livingstone. At another level, it laid bare a massive divide between America and Europe: between those who view Islamic radicalism as an existential threat and those who see a protest movement that can be integrated into democratic societies.

Elected mayor in 2000, "Red Ken" Livingstone has become notorious for his role as London's chief America-basher, Iraq war critic, friend of shadowy Islamists, and apostle of multiculturalism. He played his role flawlessly.

The great problem, he argued, was not Islamic jihad, but its American counterpart. "I think there's a real danger," he warned, "that we could repeat the days at the end of the Second World War." What days does he have in mind? The beginning of American hegemony--Washington's secret plot to dominate the world, which everyone knows set off the Cold War.

Livingstone received rabid applause for the notion that the West, particularly the United States, has invited Muslim rage because of decades of miscreant foreign policy. Worse still, he huffed, America projects a pugnacious, Manichean view of culture and politics. Its militarism toward Islam threatens to become a self-fulfilling prophecy. Livingstone's immodest conclusion: "There is no honorable basis for the foreign policy of either the United States or Great Britain."

The mayor's lodestar is multiculturalism, the active accommodation of Islamist values by Western states. He personally flaunts this doctrine, choosing as his debating partner, for example, the Islamist activist Salma Yaqoob. The pairing symbolized the macabre alliance of the political left with militant Islam: Yaqoob, who campaigns on behalf of captured terrorists, belongs to the RESPECT party--founded by George Galloway, the MP expelled from the Labour party after he "incited foreign forces" to attack British troops in Iraq.

Livingstone defended multiculturalism as outreach to moderate Islam. London, he said, is proof that his vision is working: The city boasts more language groups than any in the world, yet remains an exemplar of social integration and civic peace. "I think," he announced, "that we're at the beginning of a global civilization emerging."

Daniel Pipes, whose irenic style could not hide the magnitude of his burden, took Livingstone to task. There is indeed, he said, a fundamental clash--between those who are civilized and those who could be called "ideological barbarians." These modern-day barbarians, Pipes said, are the Muslim radicals who follow in the footsteps of European fascists and Communists. Like them, they seek to dominate through terror; to usher in a utopian vision; and to silence or destroy any murmur of dissent. Multiculturalism is not the remedy for this disease, but rather an enabler. "[Livingstone] wants everyone to get along. I want to defeat a terrible enemy."

Pipes, director of the Middle East Forum, was joined by London-based commentator Douglas Murray, author of Neoconservatism: Why We Need It. Both argued that, contrary to the portrait of London as an oasis of calm, it has become a nesting place for international terrorism. The 7/7/05 train bombings, the first suicide attacks committed by native Britons against their fellow citizens, only hint at the problem. Britain's toleration of militant preachers--who use mosques and Internet cafés to incite violence--has inspired a vast network of Islamic radicalism.

Government reports suggest that about 3,000 British-born or British-based individuals have passed through al Qaeda training camps, and that at least 16,000 British Muslims are now associated with possible terrorist activity--many based in London. Pipes reminded hecklers that terrorists have carried out, or attempted to carry out, deadly attacks in at least 15 countries. The real danger now, he warned, is that London is exporting its terrorism abroad. "London is posing a threat to the rest of the world," Pipes said. "[Al Qaeda] seeks a cosmic confrontation with the West."

That doesn't seem far off the mark. Last month, the city's Metropolitan Police commissioner, Sir Ian Blair, said the terrorist threat level was "of an unparalleled nature"--and growing. Blair cited the desire, and capacity, of terrorists to commit mass atrocities against ordinary citizens. "In terms of civilians, you would have to go back to probably either the Second World War or Cold War for that."

Multicultural policies, Pipes argued, make the problem worse by deepening a sense of alienation. Polls show, for example, that about one in four British Muslims express sympathy for the "feelings and motives" of the 7/7 bombers. A handful of politicians, such as the Labour party's Trevor Phillips, chairman of Britain's Commission for Racial Equity, have, however, pushed back: Phillips made front-page headlines in 2004 when he declared that the U.K.'s entire multicultural project had failed--thanks to its rejection of British values--and should be scrapped. "Shall we kill it off?" he asked. "Yes, let's do that."

Plenty of Londoners agree with him. Judging by their applause and howls of approval, the audience at last week's debate--probably as diverse as any in the city--named Pipes and Murray the victors. Nevertheless, it's doubtful that their arguments are gaining ground among British politicians or voters. Despite Livingstone's rationalizations for Islamist violence and his cozy relations with terrorist groups such as the Muslim Brotherhood, he was reelected mayor in 2004--and many think he'll win again if he seeks another term.

In addition, last month the Foreign Office instructed cabinet ministers to drop the phrase "war on terror" because it might offend British Muslims. A Foreign Office spokesman defended the action this way: "We tend to emphasize upholding shared values as a means to counter terrorists." And just last week, the director of public prosecutions denied that Britain was in a "war on terror" and called for "legislative restraint" to address terrorist acts.

Just what the "ideological barbarians" were hoping for.