It's rare that Jimmy Fallon gets serious.

But the Tonight Show host, who was once criticized for playing nice with then-Republican presidential nominee Donald Trump in an interview during the campaign, opened his show with a sober and heartfelt speech about the deadly violence that occurred over the weekend in Charlottesville, Va.

"Even though the Tonight Show isn't a political show," Fallon said, "it's still my responsibly to stand up against intolerance and extremism — as a human being."

Fallon initially focused on his two young kids as he recalled watching coverage of the rally that brought together white supremacists, neo-Nazis, and members of the Ku Klux Klan angry over the removal of a statue of Confederate Gen. Robert E. Lee in downtown Charlottesville, home of the University of Virginia.

But the comedian, fighting back tears, quickly turned his attention to Trump's muted comments hours after a woman was killed by a car allegedly driven by a Nazi sympathizer, and two state troopers on protest duty died in a helicopter crash. In his initial statement, the president didn't single out any of the racist groups and blamed the violence on "many sides."

"The fact that it took the president two days to come out and clearly denounce racists and white supremacists is shameful," Fallon said. "I think he finally spoke out because people everywhere stood up and said something."

Trump returned to the White House on Monday, two days after the deadly rally, and called out the "KKK, neo-Nazis, white supremacists" by name, labeling them "thugs."

But for many, Trump's prepared remarks — which began with his touting employment numbers and the administration's work on trade policies — was too little, too late.

Late Night host Seth Meyers reminded viewers that Trump began his entry into politics by claiming former President Barack Obama, the nation's first black president, wasn't born in this country.

"It was racist and insane, but he was written off as a clown, a bitter little man who didn't know an American could have a name like Barack Obama," Meyers said in the opening of his show Monday night. He continued to criticize the president for stoking racial tensions by calling Mexicans rapists during the campaign and continuing to spotlight black-on-black violence in Chicago.

"President Trump did not immediately denounce the white supremacist movement when given the chance," Meyers said. "And now, whether he knows it or not, many of those people see him as leading that movement."

After Trump's comments Saturday, many prominent white nationalists celebrated the fact that the president didn't call them out.

"He didn't attack us," wrote Andrew Anglin, creator of the Nazi website the Daily Stormer. He "implied that there was hate … on both sides. So, he implied the antifa [antifascists] are haters. There was virtually no countersignaling of us all."

"The leader of our country," Meyers said, "is called the president because he's supposed to preside over our society. His job is to lead, to cajole, to scold, to correct our path, to lift up what is good about us, and to absolutely and unequivocally and immediately condemn what is evil in us.

"And if he does not do that, if he does not preside over our society, then he's not a president."

On CBS, Late Show host Stephen Colbert, who has been an outspoken critic of the president, didn't open with the level of seriousness of his late-night colleagues. But he did ask guest Anthony Scaramucci, Trump's former White House communications director, why he thought the president failed to denounce white hate groups.

"Let's be fair to him today," Scaramucci said. "He did condemn the Nazis today."

"Two days later. Does he order his spine on Amazon Prime?" Colbert asked. "Why did it take so long?"

"That's a good line," Scaramucci shot back. "Only he can really answer that question."