Tucker Carlson warned Monday on "Tucker Carlson Tonight" that the rhetoric on the left is becoming increasingly extreme against President Donald Trump.

In a periodical called Eurasia Review, economist Robert Reich -- who Carlson pointed out has been a well-respected liberal voice for decades -- said that impeachment is not an "adequate remedy" for Trump's tenure, but that his presidency "should be annulled."

Reich has a long history in political and academic circles, serving as labor secretary under President Clinton, working as a professor, running for governor of Massachusetts and testifying against John Roberts in his Supreme Court confirmation hearing.

In the 1990s, Carlson said, Reich's views "weren't mainstream, but he certainly wasn't stupid or a hater." He added that Reich is another liberal whose politics apparently shifted toward the extreme in response to Trump.

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Carlson said that Reich's statement effectively calls for Trump to be "erased from history and forgotten by decree."

"[If] reality isn't tolerable, it should be banned," Carlson said in characterizing Reich.

He added that ex-CIA Director John Brennan reiterated his characterization of Trump as having committed "treason," adding that Brennan again accused the president of a "death penalty offense."

Carlson said that Brennan and Reich show that leftist ire toward Trump has gone from calling him a racist to calling him a traitor to calling him a "non-person who must be erased from our collective memory."

"The left is out of epithets, all that's left is physical harm," Carlson warned.

Watch more in the segments above, including reaction from Mark Steyn. 

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