JK Rowling, Salman Rushdie and Margaret Atwood are among the signatories to a controversial open letter warning that the spread of “censoriousness” is leading to “an intolerance of opposing views” and “a vogue for public shaming and ostracism”.

Rowling, whose beliefs on transgender rights have recently seen scores of Harry Potter fans distance themselves from her, said she was “proud to sign this letter in defence of a foundational principle of a liberal society: open debate and freedom of thought and speech”.

Rowling compared the current climate to the McCarthy years, adding: “To quote the inimitable Lillian Hellman: ‘I cannot and will not cut my conscience to fit this year’s fashions’.”

Published in Harper’s Magazine, the letter is signed by more than 150 writers, academics and artists, also including major names such as Martin Amis, Noam Chomsky, Steven Pinker, Malcolm Gladwell and Gloria Steinem.

Acknowledging that “powerful protests for racial and social justice are leading to overdue demands for police reform, along with wider calls for greater equality and inclusion across our society”, the letter goes on to decry what it calls “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”.

Hitting out at how a “panicked damage control” is leading to the delivery of “hasty and disproportionate punishments instead of considered reforms”, the letter criticises how “editors are fired for running controversial pieces; books are withdrawn for alleged inauthenticity; journalists are barred from writing on certain topics; professors are investigated for quoting works of literature in class; a researcher is fired for circulating a peer-reviewed academic study; and the heads of organisations are ousted for what are sometimes just clumsy mistakes”.

Its instigator, the writer Thomas Chatterton Williams, referenced incidents including the allegations of racism which led to resignations at US institutions like the National Book Critics Circle, and the Poetry Foundation, to the New York Times.

“Donald Trump is the Canceler in Chief,” Williams told the NYT. “But the correction of Trump’s abuses cannot become an overcorrection that stifles the principles we believe in.”

The letter ends with the writers asserting that “the way to defeat bad ideas is by exposure, argument, and persuasion, not by trying to silence or wish them away”.

It has been met with criticism online. “As is usually the case for people who manifest in favor of free and open debate and against repression, several of the people on this @Harpers Open Letter have behavior in their past that reflects the censorious mentality they’re condemning here,” tweeted the journalist and author Glenn Greenwald.

For the US senator Brian Schatz, his take on the letter was “that lots of brainpower and passion is being devoted to a problem that takes a really long time to describe, and is impossible to solve, and meanwhile we have mass preventable death”.

One of the original signatories to the letter, historian Kerri Greenidge, said she did not endorse it and was asking for a retraction. Her sister, the author Kaitlyn Greenidge, said she had been sent the letter and asked to sign it, but had declined. She told Harper’s, in a reply she shared online, that she did not “subscribe to the concerns in this letter and do not believe this threat is real. Or, at least, I do not believe being asked to consider the history of anti blackness and white terrorism when writing a piece, after centuries of suppression of any other view in academia, is the equivalent of a loss of institutional authority.”

Another signatory, writer Jennifer Finney Boylan, said she had not known who else had signed the letter. “I thought I was endorsing a well meaning, if vague, message against internet shaming. I did know Chomsky, Steinem, and Atwood were in, and I thought, good company. The consequences are mine to bear. I am so sorry.”

Williams said that one of the criticisms levelled at the letter was that it was a list of people who are scared, showing they fear change. This was not the case, he said.

“No, this is people who are concerned about an intolerant climate and believe justice and freedom are inextricably linked. The scared people declined to sign,” he wrote on Twitter. “And of course that is not to say that EVERYONE who declined to sign did so out of fear. There were very instructive conversations and disagreements. People really see things differently. But some not insignificant number of people agreed but said they feared the repercussions.”

He told the New York Times: “We’re not just a bunch of old white guys sitting around writing this letter. It includes plenty of Black thinkers, Muslim thinkers, Jewish thinkers, people who are trans and gay, old and young, right wing and left wing. We believe these are values that are widespread and shared, and we wanted the list to reflect that.”