When Heritage Foundation President Kevin Roberts posted a controversial video in October defending Tucker Carlson and his interview with neo-Nazi influencer Nick Fuentes, Ben Shapiro quickly became one of the most prominent conservative voices criticizing the venerable conservative think tank.

Shapiro furthered that criticism in a fiery speech on Wednesday at the Heritage Foundation’s Washington headquarters, where he called on the institution to draw lines against Carlson and ensure that the right-wing podcaster is not considered to be part of the conservative movement. 

“I want to begin by acknowledging the elephant in the room. The conservative movement is in flux. It’s in flux because of the systemic failure by conservative leaders to do what any good leaders must do: define and maintain the foundations of that movement,” said Shapiro, who had previously called out Heritage in a November episode of his podcast. “This is our job.”

Shapiro, who has supported President Donald Trump’s efforts to cut down on immigration, used immigration enforcement as an analogy for how the conservative movement should define the acceptable boundaries of debate.

“No country can exist without borders and no conservative movement can exist without principles it will defend against those who degrade them, even from within,” Shapiro argued. “The Heritage Foundation has always been the institution defining the contours of conservatism. If the Heritage Foundation wishes to retain its status as a leading thought institution in the conservative movement, it must act as ideological border control. It must continue to draw the contours of legitimate, real conservatism. This is what the institution exists to do.”

Shapiro, who has been affiliated with Heritage for years, described the think tank as “perhaps America’s leading institution in helping to define and shape the contours of conservatism.” But what followed was a word of warning, cautioning Heritage that continuing to align with people like Carlson will ruin the conservative movement.

“If, as the Heritage Foundation proclaims, our goal ought to be to formulate and promote conservative public policies based on the principles of free enterprise, limited government, individual freedom and traditional American values and a strong national defense,” Shapiro stated, “then we must stand up against those who would pervert and twist the conservative movement into a movement without principles, or worse, a movement that promotes the very opposite of the principles that conservatives hold dear.”

Over the next 20 minutes, Shapiro laid out exactly why believes Carlson and his conspiratorial worldview run counter to the ideals of American conservatism: Carlson called on America to ally with Russia; Carlson “has unending critiques of the free market, mirroring Marxist thinkers”; Carlson “promotes a conspiracy theory by which the American people have lost total control of their lives and thus have no real ability to shape policy”; Carlson has spoken of Iran with admiration and treated Qatar “as America’s foremost ally in the Middle East”; and he has hosted “America’s foremost Hitler apologist,” Nick Fuentes. 

“The term ‘American conservatism’ has a meaning. That meaning is embodied in the Heritage Foundation’s mission statement,” said Shapiro. “Those who oppose those principles definitionally oppose American conservatism. That is just definitional. Such people are not ideological allies. They are not part of the rich debate that is constantly ongoing between various strands of conservatism. They are opponents, and they ought to be treated that way.”

Welcoming those opponents as if they are part of legitimate debate over conservative ideas does a disservice to the political cause, Shapiro argued.

“Which brings us,” he added, “to Tucker Carlson, who has become, by any honest assessment, an opponent of conservatism, an outsider masquerading as an insider and destroying the character of the conservative movement in the process.”

At the end of his speech, Shapiro talked about what he described as “the promise of conservatism and the promise made by the Heritage Foundation,” that Americans should consider themselves lucky to be in this country and that they have agency to chart their own destiny. 

“That promise only exists if conservatives do our job to draw lines, to create borders, to protect our principles, to defend those principles, to conserve,” he said.

Afterward, Roberts joined Shapiro onstage for a moderated conversation. He did not address the content of Shapiro’s speech, or anything he said about Carlson.

“You and I agree far more than we disagree on things, and the disagreement is truly friendly,” said Roberts, who has been navigating internal dissent and staff defections following his video defending Carlson. 

Later, before the conversation wrapped up, Roberts said to Shapiro: “Count on Heritage to fight with you.”