He's crossed swords, over the years, with all the usual right-wing suspects, from car-makers to gun owners to Wall Street executives, health companies, and George W Bush. Now Michael Moore has picked a fight with a hero of the international left.
The documentary-maker has caused outrage among Hugo Chavez's supporters by using a late-night chat show to tell a humorous anecdote about meeting Venezuela's socialist President in a luxury hotel suite during the recent Venice Film Festival.
His two-minute yarn, told to ABC host Jimmy Kimmel earlier this month, seemed harmless enough. Moore alleged that he and his wife had been woken at 2am by a racket coming from Mr Chavez's room and ventured upstairs to ask him to quieten down.
"A bottle and a half of tequila later," Moore claimed, he had helped the President to write the speech he recently delivered to the UN. "At the very least, the guy owes me a year's worth of free gasoline!" he joked.
But there was a problem with the story. A big one. The meeting that Moore so confidently described never happened. And tequila certainly wasn't consumed: Mr Chavez is teetotal.
The duo did meet in Venice, but only in the daytime. Moore, in town to launch his new film, Capitalism, sat with Mr Chavez, who was there to promote Oliver Stone's documentary South of the Border, for three hours. The US press were excluded from the meeting.
Supporters of Mr Chavez now suspect that Moore fabricated his anecdote to gloss over the chummy nature of that encounter. They have taken to the airwaves in a Monty Python-style PR offensive, to accuse Moore of betraying a supposed comrade.
"Michael Moore is a most unfortunate coward," declared blogger Eva Golinger. She dubbed him "the worst of yellow journalists, a liar and storyteller on the big screen", and said his yarn was "offensive and insulting" and a clear sign of his "hypocrisy and lack of ethics". Franz JT Lee, a Marxist academic and blogger, claimed that the film-maker's comments were "part of the United States' 'war of ideas'" against Venezuela, and said similar "propaganda" led to the rise of the Nazis in 1930s Germany.
They didn't just spark outrage on the left, though. Critics of Mr Chavez have called the level of invective against Moore – some of which was aired on Venezuelan state television – disproportionate. They believe his anecdote was intended to be a harmless, tongue-in-cheek joke. The socialist movement failed to grasp the nuances of his intended irony, they claim, because they lack a sense of humour.
Quite what the affair says about the integrity of Moore and his documentaries remains to be seen. The film-maker has declined to comment or apologise for misleading TV viewers, save for a brief message posted on his Twitter feed on Monday: "For the record, the President of Venezuela doesn't drink."