Harper’s letter asserts way to ‘defeat bad ideas is by exposure, argument, and persuasion’, but critics accuse authors of censorious mentality

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”.