There was no plane crash on the Pentagon on September 11: this is what French writer Thierry Meyssan alleges in a book that has become a bestseller across the Channel.

In L'Effroyable Imposture (The Dreadful Imposture), Meyssan ludicrously alleges that no witness can claim to have seen a plane crash into the building (it was an inside job really), There was also a secret CIA base in the World Trade Center, he claims.

Meyssan also "reveals" America's hidden agenda on the war on terrorism.

So what's new? A nutcase has come up with a classic the-American-military-industrial-complex-is-really- responsible-for-it-conspiracy theory.

That Meyssan is alleging such preposterous theories is pathetic, but he would not be the first idiot to claim to know the truth.

What is shocking about this book is that it is selling well - very well - in France: 100,000 copies in a week, according to the French news daily Libération, which also reports that the book's publisher has run out of copies.

This allows the Today programme editor, Rod Liddle, in today's Guardian to make sweeping generalisations about how French people "may have a greater capacity for thinking big thoughts but unfortunately they possess also a greater propensity to believe them, even when they are demonstrably nonsense".

Well, guess what Rod? We don't. Not every French person swallows these theories.

First, Meyssan is not a "respected commentator from a left-liberal thinktank".

Yes, he has variously been involved, according to Le Monde, in freemasonry, a leftwing party and is the president of another leftwing organisation called Réseau Voltaine.

But the latter is hardly a highly-established thinktank, more like a minor pressure group.

And to call Meyssan an "established commentator" is like saying that my aunt Jacqueline is an authority on the Israeli-Palestinian conflict (she is not).

Moreover, the French media have been at pains to investigate Meyssan's allegations point by point prove that they were indeed ludicrous.

The only reason The Dreadful Imposture left the internet rumour mill to reach a wider audience was because Meyssan was invited on showbiz television show Tout le Monde en Parle (Everybody is talking about it), a show that is more concerned with creating scandals than journalistic investigation.

True, large numbers of people have bought the book. Does that automatically mean they believe Meyssan's theories, or that they are gullible enough to believe his argument? No.

So please Rod, don't make dreadful generalisations about French people. There are enough going around already.