Jon Stewart Returns to Late Night, Delivers a Blistering Defense of Jimmy Kimmel and a Scathing Rebuke of Trump.

LOS ANGELES — On Thursday night, Jon Stewart made a rare return to the late-night desk he left a decade ago, and he wasted no time reminding viewers why his absence has felt, to many, like a national emergency.

Appearing as a guest host on “The Daily Show,” Mr. Stewart used the full force of his rhetorical arsenal to defend his friend Jimmy Kimmel, whose ABC program has been under sustained attack from President-elect Donald J. Trump, and to issue what may be the most surgically precise takedown of Mr. Trump’s second presidency before it has even begun.

The segment began quietly enough. Mr. Stewart, silver-haired and visibly energized, leaned into the camera and said, almost conversationally, “I came back for one night because someone has to say this out loud: threatening television hosts is not ‘owning the libs.’ It’s authoritarianism with a spray tan.”

What followed was twelve uninterrupted minutes of controlled fury, a reminder of the comedic and moral clarity that once made “The Daily Show” appointment viewing for an entire generation of politically attuned Americans.

Mr. Stewart’s central argument was straightforward: Mr. Trump’s repeated threats to use the levers of government — including the Federal Communications Commission — against broadcasters who mock him represent a dangerous escalation in the long war between the president and the press. He cited Mr. Trump’s Truth Social posts from the past week, in which the president-elect suggested that ABC’s license should be revoked because Mr. Kimmel had “gone too far” in a monologue that featured a parody of the iconic Iwo Jima flag-raising photograph, only with a Trump campaign flag replacing the Stars and Stripes.

“Jimmy didn’t storm a beach,” Mr. Stewart said, pausing for effect. “He stormed a punch line. And apparently that’s now a federal crime.”

The audience roared. But Mr. Stewart was just warming up.

He then pivoted to a broader indictment, tracing a through line from Mr. Trump’s 2016 attacks on the cast of “Hamilton” to his recent vows to “open up the libel laws” and his appointment of Brendan Carr, a known critic of Big Tech content moderation, as the next F.C.C. chairman. “This isn’t about hurt feelings,” Mr. Stewart said. “This is about power. The kind of power that decides which voices get amplified and which ones get silenced.”

Perhaps the most memorable moment came when Mr. Stewart addressed Mr. Trump directly, a device he used to devastating effect during his original 2000–2015 run. Looking straight into the lens, he said: “You spent years telling us the media was the enemy of the people. Fine. But late-night comedy? We’re not the enemy of the people. We’re the people who remind the people when their leaders are acting like clowns. And right now, sir, the red nose is on you.”

The studio audience rose to its feet.

Behind the scenes, the appearance had been arranged at the last minute. According to two people with knowledge of the booking, Mr. Kimmel personally called Mr. Stewart on Tuesday evening after receiving what he described privately as “yet another unhinged voicemail” from Mr. Trump. Mr. Stewart, who has largely stayed out of the daily political fray since handing “The Daily Show” to Trevor Noah in 2015, agreed immediately.

The result was a rare display of late-night solidarity. At the end of the segment, Mr. Kimmel joined Mr. Stewart via satellite from his Los Angeles studio. The two men, who have been friends for three decades, shared a quiet moment of gratitude before Mr. Kimmel said simply, “Thank you for having my back.” Mr. Stewart replied, “Always. That’s what friends do. And that’s what a free country is supposed to do.”

By Friday morning, the clip had been viewed more than 28 million times across platforms, a number that rivals the most viral moments of the 2016 campaign. Hashtags like #StandWithKimmel and #JonIsBack trended for hours. Perhaps more telling was the silence from Mar-a-Lago; as of Thursday night, Mr. Trump had not responded publicly to the segment, a departure from his usual rapid-fire retorts.

For many observers, Mr. Stewart’s return felt less like a nostalgic cameo than a necessary intervention. In an era when democratic norms are being tested daily, his performance served as both a reminder of what principled comedic outrage can achieve and a warning of what may be lost if such voices are intimidated into silence.

As Mr. Stewart signed off, he left the audience — and the country — with a final thought: “Comedy isn’t courage. But defending it might be.”

Whether that defense will be enough in the years ahead remains an open question. For one night, at least, Jon Stewart made the answer feel slightly less uncertain.