The left-wing author and activist stunned BBC Newsnight host Evan Davis by suggesting the policies of President Donald Trump’s party make them worse than jihadis and dictatorships.
Mr Davis quizzed Mr Chomsky about his previous claims the Republican party is the “most dangerous organisation on earth” over their economic policies and views on climate change.
But Mr Chomsky corrected his interviewer, saying they are, in fact, the most dangerous organisation “in human history.”
The 88-year-professor adds: “It’s a very outrageous statement but is it true?”
A stunned Mr Davis asks his guest if he rates them “worse” than missile-obsessed North Korea or bloodthirsty ISIS.
Mr Chomsky asks: “Is ISIS dedicated to trying to destroy the prospects for organised human existence?
“What does it mean to say, ‘we’re not doing anything about climate change, we’re trying to accelerate the race to the precipice’.”
President Trump’s administration has been divided over plans to pull the US out of a major climate pact.
The US Commander-in-Chief vowed during his presidential campaign he would “cancel” the Paris climate agreement, signed by nearly 200 countries in 2015.
Senior White House figures such as chief strategist Steve Bannon want to pull out of the deal, while secretary of state Rex Tillerson and Mr Trump’s daughter Ivanka want the US to remain.
Meanwhile, former President Barack Obama delivered a speech in Milan warning against the perils of climate change.
He said Earth is not “condemned to ever rising temperatures”, but added: “Nobody can sit on the sidelines if we want to deal with this issue in an effective way.”