Here we go again, sliding dangerously down The Bell Curve. On the eve of a British speaking tour, James Watson, the DNA pioneer and Nobel laureate, has claimed that Africans are less intelligent than whites, a theory explored by the notorious 1994 book The Bell Curve. The Science Museum in London has cancelled Professor Watson’s sell-out speaking engagement tonight, on the ground that his views have gone “beyond the point of acceptable debate”. A spokesman also claimed that “the Science Museum does not shy away from debating controversial topics”.

The intellectual cowardice of the cancellation strikes at the heart of what science stands for: the full and free exchange of scientific ideas. The Science Museum says that it does not want to provide a platform for scientific racism, but its actions have ensured that the professor has gained worldwide publicity and, quite possibly, sympathy.

Watson is not an avuncular elder statesman of science: he has argued that parents should have the right to abort a foetus with a genetic tendency towards homosexuality. The museum knew it was getting a controversial old dinosaur.

But Watson must be challenged robustly on his views and pushed to provide the evidence; in London, at least, he will no longer have to account publicly for his comments. Apart from denying us the chance to see Watson squirm, trying to keep a lid on controversial ideas is rarely a wise move. Suppression is the lifeblood of conspiracy theories; why is the scientific community so desperate to silence Watson? Some may infer it is because he is the revealer of an unsayable truth, just as some parents believed wrongly that the MMR-autism theory must be right when public health officials refused to appear on the same platform as Andrew Wakefield, the doctor who had ignited the vaccination furore. When you shut down an idea, people listen at the door for whispers. Now that the internet can be employed by any crackpot to disseminate the most ludicrous hypotheses, a stifled debate quickly becomes a source of flaky science, rumours and half-truths.

The same commitment to openness demands that I defend the right of the British National Party to publicise its miserable policies – only by watching its halfwits in action can you comprehend the unedifying extent of their smallmindedness. If you believe in free speech you have to take the chaff with the wheat.

As well as intellectual cowardice, the Science Museum is guilty of hypocrisy. On October 30, it will hold an event called Is Science Colour-Blind? “Might race have a useful role to play in contemporary science? Talk about the legacies of scientific racism today . . .” runs the blurb. You know what? The museum had a perfect opportunity to do exactly that tonight – and blew it.

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