LONDON — Anti-Americanism is not only the world’s most pernicious and ubiquitous ideology — it is also the most tenacious. In fact, it has taken on some aspects of a religion.

Richard Dawkins thinks God is a delusion. He is mistaken, of course: people are deluded when they worship idols. But the worst idol of our time is anti-Americanism. Its devotees will fit any facts into their all-embracing faith in the unique wickedness of the Americans — the people that, of all the nations on earth, least deserves to be demonized in this way.

This week I attended a debate in London on the motion that “America has lost its moral authority.” The members of the audience were highly educated, prosperous (they were paying $50 a ticket), and the event was sponsored by the right-of-center Spectator magazine.

So the Royal Geographical Society theatre was not full of Noam Chomsky wannabes. Yet before the debate even began they voted for the motion (i.e., against America) by 431 to 143, with 176 undecided.

Anti-Americanism is not the monopoly of the Left. In fact, it is strongest among the British liberal establishment, which is saturated in BBC propaganda.

That was true of the speakers, too. The only one of those supporting the motion who could be described as left-wing was the novelist Will Self. And he was the only one on either side who has a U.S. passport. The others were the columnist Matthew Parris and the author John Gray. Mr. Parris writes for the London Times — owned by Rupert Murdoch and one of the few British newspapers not to succumb to anti-Americanism. Mr. Gray was a professor at Oxford and the London School of Economics.

Yet their speeches were dripping with hatred and contempt for America. Mr. Self claimed that American politics was so corrupt that “you would have to be a pedophile to lose your seat in Congress.” He claimed that, on average, 98% of the members of Congress were reelected, which, as the Columbia University-based historian Simon Schama pointed out, means that power never changes hands and makes America a one-party state. And, sure enough, Mr. Self compared America both to the Soviet Union and to Nazi Germany. He also claimed that living standards for the poorer Americans were “worse than in Syria,” which nobody bothered to correct.

Then came John Gray, for whom America is defined by one thing: torture. He tried to scare the audience with detailed descriptions of waterboarding, ignoring the fact that the reason we know all about it is that America is one of the few countries in which officials are held accountable for their use of coercive techniques.

Finally, there was Matthew Parris, whose account of American history is a story about land-grabbing, genocide, and slavery is as cynical as it is inaccurate. He sneered at the “lickspittle British Atlanticists” (I think he meant people like me), but his real animosity was directed at the American people rather than their government. President Bush and his neocons, Mr. Parris declared, were not the antithesis of the American dream, but part of it — indeed the “distillation” of that dream.

And what of the defense? Mr. Schama did a good job of correcting the most egregious errors: “I stopped listening to Matthew Parris when he mentioned that George Washington lived at a place called ‘Montibello.’ It was, of course, Monticello and the man who lived there was Jefferson.” But Mr. Schama is so hostile to the Bush administration that he was too apologetic to be a good apologist.

Martin Amis, the novelist, was more robust in his defense. He cited Bosnia, Kosovo, Kuwait, Lebanon, Pakistan, and all the nations afflicted by the 2004 tsunami as beneficiaries of American generosity. He deployed his accustomed eloquence to denounce “unadorned anti-Americanism.” But, he too, conceded too much. “Good intentions are decisively better than bad intentions,” seems a trifle understated, even by British standards.

So it was left to another writer, Howard Jacobson, to get down in the dirt and give the anti-Americans a good kicking. “America has ceded the moral high ground — to whom, precisely?” he asked. His withering words about the gloating of European intellectuals over American misfortunes will live long in my memory. He even cited Mr. Gray’s own words against him: “You asked when Jews will be forgiven the Holocaust. Well, when will Americans be forgiven 9/11?”

By the end of the debate, the case for the defense had won. If it was not an actual victory, at least it was a moral one. The final voting figures were: 433 for the motion, 291 against. So the pro-American camp had won over almost all the undecideds (including my 16-year-old daughter Edith), more than doubling their vote. Not a single one of the anti-Americans had been persuaded, and they were still in the large majority.

That is a measure of the problem we Atlanticists face: here in Britain, in Europe, and around the world. It is not a problem that a new president will solve by him or herself.

For what it was worth, the speakers predicted either Senators Obama or McCain to win in November, but none of them thought it would make a big difference to the way America is seen abroad.

Anti-Americanism is a pathological symptom, not a rational analysis. It would be a grave mistake for Americans to cast their votes for the candidate they thought would make America more likeable abroad. That would be a blow to the respect for which America still holds from its many friends and admirers.

Mr. Johnson is the editor of Standpoint magazine.