"Individuals, not any institution or group, should make their own judgments about ideas and should express these judgments not by seeking to suppress speech, but by openly and vigorously contesting the ideas they oppose, without discrimination or intimidation.
"We must ensure that our higher learning establishments are places where intellectual rigour prevails over emotional blackmail and where academic freedom, built on free expression, is maintained and protected. We must fight for each other's right to express opinions, even if we do not agree with them."
The letter was in response to Human Rights Commissioner Dame Susan Devoy's call for a review of "hate speech" law. Police are suggesting it be looked at as a specific crime.
Moon, told the Herald free speech at universities should be defended.
"The trouble is we often don't know the difference between free speech and hate speech," Moon said.
"Usually, if people are offended by what is said it's seen as hate speech. That's dangerous.
"It is dangerous to silence someone just because we don't like what they say."
Moon said such views are a threat to the right to free speech.
"It puts the definition of free speech at the whim of people pursuing that line," he said.
Signatories in the letter also included former Prime Minister Sir Geoffrey Palmer, commentator Sir Bob Jones, academics, business leaders and community representatives.
Freedom of speech, Moon said, was the foundation of a modern, diverse and democratic society.
It protected religious freedom and individual expression, he said.
Moon said kneejerk calls from police and the Human Rights communision to introduce hate-speech laws will have the unitended consequence of suppressing free speech.
"It will create a culture of fear," he said.
"What we need is open debate, which will change racist and intolerant views, not censorship."
Moon said freedom of speech was intimately connected with freedom of thought.
He believed the law in New Zealand was working well, and need not be changed.
Moon said the forced closure of the European student club at Auckland University and threats to its members was something to be wary of.
"If what they say is indeed racist or promoting hate, then we should expose and ridicule it, not just shut it down," he said.
Moon said he planned to send a copy of the letter to all party leaders in Parliament.
People who put their name to the letter were:
Assoc Professor Len Bell, Dr Don Brash, Dr David Cumin, Sir Toby Curtis, Dr Brian Edwards, Graeme Edwards, Dr Gavin Ellis, Sir Michael Friedlander, Alan Gibbs, Dame Jenny Gibbs, Bryan Gould, Wally Hirsh, Professor Manying Ip, Sir Bob Jones, Professor Pare Keiha, Assoc Professor Luamanuvao Winnie Laban, Dame Lesley Max, Gordon McLauchlan, Professor Paul Moon, Sir Douglas Myers, Assoc Professor Camille Nakhid, Sir Geoffrey Palmer, Professor Edwina Pio, David Rankin, Philip Temple, Dame Tariana Turia and Professor Albert Wendt.