Jimmy Kimmel on Tuesday challenged President Donald Trump to back up a claim he constantly makes about Americans who protest against him.

“These are paid insurrectionists. These are paid agitators,” Trump said in a Fox News interview.

Kimmel’s studio audience booed the president.

“I believe he believes it,” Kimmel said. “He can’t imagine anyone ever doing anything without getting paid for it.”

Kimmel defended the protesters as “concerned Americans,” then had a message for the president.

“If they’re paid agitators, by the way, prove it,” Kimmel said. “You keep saying they’re paid agitators? Prove it.”

Kimmel said he could think of at least one person who fits the bill.

“You know who is a paid agitator? You are!” he fired back. “You literally sold a crypto coin that says ‘fight, fight, fight’ on it. You’re a paid agitator surrounded by a bunch of greasy little paid agitator-tots.”

See more in his Tuesday night monologue: