“Harry Potter” author J.K. Rowling, cognitive scientist Noam Chomsky and other figures signed a public letter on Tuesday warning about the “restriction of debate” in society.

The open letter, which has gathered 150 signatures from activists and writers, warns that the “free exchange of information and ideas” is “daily becoming more constricted.” The letter was published on the Harper’s Magazine website and will be featured in the magazine’s October issue.

The signatories say in the letter that the “needed reckoning” of racial and social justice has “also intensified a new set of moral attitudes and political commitments that tend to weaken our norms of open debate and toleration of differences in favor of ideological conformity.”

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“While we have come to expect this on the radical right, censoriousness is also spreading more widely in our culture: an intolerance of opposing views, a vogue for public shaming and ostracism, and the tendency to dissolve complex policy issues in a blinding moral certainty,” they add.

“This stifling atmosphere will ultimately harm the most vital causes of our time,” the letter continues. “The restriction of debate, whether by a repressive government or an intolerant society, invariably hurts those who lack power and makes everyone less capable of democratic participation.”

It also condemns the “hasty and disproportionate punishments” against editors, writers, journalists, professors, researchers and others who have covered “controversial” topics or make “clumsy mistakes.”

The letter criticizes President TrumpDonald John TrumpUSPS warns Pennsylvania mail-in ballots may not be delivered in time to be counted Michael Cohen book accuses Trump of corruption, fraud Trump requests mail-in ballot for Florida congressional primary MORE as well, saying that “the forces of illiberalism ... have a powerful ally” in the president, “who represents a real threat to democracy.”

Rowling promoted the letter Tuesday on Twitter, saying she was “very proud” to sign it.

“I was very proud to sign this letter in defence of a foundational principle of a liberal society: open debate and freedom of thought and speech,” she tweeted.

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The “Harry Potter” author has been embroiled in controversy recently after being criticized for making comments about the transgender community that many have called transphobic.

The president also discussed "cancel culture" in his speech at Mount Rushmore last week, calling it a "political" weapon.

“One of their political weapons is ‘cancel culture’ — driving people from their jobs, shaming dissenters and demanding total submission from anyone who disagrees,” he said at the Fourth of July celebration. “This is the very definition of totalitarianism.”