When I was researching You Can't Read This Book, my study of censorship, an old joke came back to me. "You can be a famous poisoner or a successful poisoner but you can't be both".
Successful censorship is hidden. A writer who concentrates on the famous cases misses the point. Censorship everyone knows about is not successful precisely because everyone knows. One can understand the suppression that matters only when one thinks about the books that are never written and the arguments that are never made.
Alarmingly, considering the virulence of its antisemitism, radical Islam is too hot to handle. Its ideology cannot be mocked as those of Christianity and Judaism have been since the Enlightenment. The stories about its prophet cannot be exposed as fables, as with Jesus and Moses. The reason is simple: writers are frightened, above all of violence.
No one wants to go through what Salman Rushdie went through. But the success of terror in intimidating is not the sole reason for the paralysis. With good cause, people are frightened of helping racists who do not oppose extremism out of any concern for gay or women's rights or the rights of free people to believe what they want, but because they hate Muslims because they are Muslims. Yet, by refusing to tackle religious fanaticism with the necessary rigour, western liberals betray Muslim and ex-Muslim liberals, who need help in their struggle against the bigots who would oppress them.
During the Danish cartoon crisis, South Park tried to show an innocuous image of Mohammed. "It's open season on Jesus," creators Trey Parker and Matt Stone said. "We've had him say bad words… shoot a gun…kill people." Yet they could do nothing with Mohammed because Comedy Central was "afraid of getting blown up". Grayson Perry, who produces what Catholics would see as blasphemous images of the Virgin Mary, told journalists he had "not gone all-out attacking Islamism in my art… because I feel the real fear that someone will slit my throat".
Such is honesty is rare because candour destroys the great pose of reporters, artists and writers, who want the public to see them as "edgy" and fearless speakers "of truth to power" - as if they were dissidents in a dictatorship. Admission of fear would leave their courageous image in tatters.
Before my book was published, the publicists called me in. "Radio 4, Andrew Marr, the Today programme, Woman's Hour, they'll love this," they said. "The power of religion, big money and the state to silence legitimate debate… it's a BBC editor's dream."
"You haven't understood me," I told them. "Radio 4 can never admit that self-censorship exists." Sure enough, Andrew Marr and the rest of them told my publishers very firmly that they would not touch the book.
The Telegraph's Cristina Odone reported that when she suggested me to a BBC executive, he replied, "Are you kidding? A white, middle-class, middle-aged man?" A BBC documentary on censorship could, apparently, only be "delivered by Diane Abbott. Even better if she converts to Islam".
His joke revealed a dismal truth. We need to be braver; not just against religious militancy but in taking on the power of the City and oligarchs to use libel laws to cover economically disastrous blunders, and the power of employers to threaten whistleblowers who speak in the public interest with dismissal. The first step is the most essential. Before we can move forward, we must find the courage to admit we are afraid.