When most authors do a reading they get a few dozen devotees in a chilly bookshop. Michael Moore, the American filmmaker turned best-selling polemicist (of Bowling for Columbine and Stupid White Men fame), is so huge that, when he promotes a book in Britain, he needs consecutive sittings at the London Palladium - and even they don't leave a spare seat in the house.

Moore does very little performance: just him, a shlubby guy in baseball hat standing by the microphone. He riffs on a few themes, reads a chapter of his book and then takes a lot of questions.

He does pack a few great lines. He urges Britons to be brave enough to sack Tony Blair: the left has nothing to fear from the Tories, who are deader than dinosaurs. "Come on, buck up here. You used to be brave and bold and send Australians into battle."

He notes that United States Vice-President Dick Cheney's former company, Halliburton, has won several contracts to rebuild Iraq. If American and British soldiers are dying for Halliburton, "then it's only fair that for every kid that dies, Halliburton has to slay a mid-level executive".

He hits all the buttons his audience want pressed: Tony Blair must go, George Bush is evil, Rupert Murdoch should be struck down by a thunderbolt. But the evening leaves a couple of reasons for a progressive not to feel so cheerful.

First, it may come naturally to the right wing to have guru figures such as American shock-jock Rush Limbaugh, with his legions of "dittohead" followers. But the bow-down homage to Moore that precedes each audience question, coupled with Moore's own bragging about his phenomenal book sales and website traffic, feels incongruous for a gathering of the left.

Second, what Moore serves up is political comfort food. There's no shame in that: he's trying to reach the masses turned off by politics. But the audience, lapping up a black-and-white view of the world in which lefties like them are goodies and everyone else is stupid, cannot let themselves off so easily.

"What Moore serves up is political comfort food. He's trying to reach the masses turned off by politics." They ought to do better than this.