Salman Rushdie has said that “the guardians of freedom of speech are to be found in publishing” and that “it falls to us to hold the line” as he opens this year’s Frankfurt Book Fair.

The choice of Rushdie as guest speaker at the world’s largest publishing event had angered the Iranian ministry of culture, which cancelled its participation in the book fair saying that “fair officials chose the theme of freedom of expression, but they invited someone who has insulted our beliefs”. Iran placed a fatwa on Rushdie after publication of his 1988 novel The Satanic Verses, forcing the Booker-winning novelist into hiding for years.

This morning in Frankfurt, the novelist spoke of how freedom of expression is being challenged by violence and threats against those in the books industry, from writers and translators to publishers and booksellers.

“Publishers and writers are not warriors, we have not tanks. But it falls to us to hold the line,” he said, according to a report in The Bookseller.

“Literature may be weak because it has no real power in the world, but in a way it is the grandest narrative of all, in that it puts ourselves into question with fiction. We challenge ourselves and refuse to take the world as a given. We challenge all correctives of opinion, all appeasements, all fears. Literature is the unafraid form.”

Yesterday, Rushdie spoke out on Twitter in support of Nayantara Sahgal and the other Indian winners of the Sahitya Akademi award who have recently returned the award in protest at the murder of the scholar MM Kalburgi in August.

“I support #NayantaraSahgal and the many other writers protesting to the Sahitya Akademi. Alarming times for free expression in India,” wrote Rushdie on Twitter, adding that he supports “no Indian political party & oppose all attacks on free speech. Liberty is my only party.”

In Frankfurt today, he said that “it is important that we defend writers as well as writing”, and that “fiction is the narrative which contests the world”.

“We should not need to talk about freedom of speech in the west. It should be like the air we breathe. It seems to me that the battle was won a couple of hundred years ago … the fact that we have to go about fighting this battle is the result of more regrettable recent phenomenon,” said the novelist, The Bookseller reported.

The organisers of the Frankfurt Book Fair have said that they hope for “further dialogue” with the Iranian ministry of culture over its cancellation of its national stand at the fair. “Several” Iranian publishers are still present in Frankfurt, according to the fair’s organisers.

Juergen Boos, director of the fair, said he hoped the cancellation was “just a brief interruption in the existing conversations and that we can continue to expand on the established relationships”, and that the event was “a place of dialogue”.

But he added: “Nevertheless, for us, freedom of expression is non-negotiable. We must not forget that Rushdie is still being threatened with death for his work.”

At today’s opening conference, Boos added that “Freedom of speech is currently in a very fragile state. It is under fire, in the truest sense of the words. The times we’re living through are defined by violent conflicts, with the violence seemingly always spiralling in one direction: the wrong direction.”

He called on the books industry to “unsettle” readers. “Look at Rushdie. He causes disturbances with his literature. And publishers, too, should unsettle and create stumbling blocks – in their portfolios and with the courage to be controversial,” said Boos, pointing to a moment in Rushdie’s new novel Two Years, Eight Months and Twenty-Eight Nights, when two centuries-old opponents talk through their contradictory standpoints.

Rushdie writes: “We can discuss these things the way we should: be polite to the opponent, but stern with the subject matter.”

“What he’s saying here is quite simple, but all the truer for that. It’s impossible anyway to kill an idea or an attitude. It won’t disappear, even if you were to murder all the people who utter the idea. What remains are always the words,” Boos told the book fair.