The tragedy of Gilles Bernheim is symptomatic of a wider hypocrisy where issues of intellectual dishonesty are concerned.

In 2009 Bernheim became chief rabbi of France. He ought to have served seven years. Last week he tendered his resignation, triggered by revelations relating to instances of plagiarism and an accusation that he acquiesced in the incorrect public characterisation of his academic credentials.

I need to make it crystal clear that plagiarism - passing off the writings and ideas of others as one's own - is nothing more or less than intellectual theft. So far as the world of scholarship is concerned it is also, unfortunately, a growth industry, facilitated by technologies that permit the unscrupulous, without attribution, to "copy and paste" written material stolen (there is no other word for it) from the writings of others.

In its simplest form this type of academic deceit is now reasonably easy to spot: there is software that can facilitate detection, but I routinely demonstrate to my students how a simple Google search can often suffice. Less easy to recognise is the bespoke essay-writing service. Where I suspect this has been used (perhaps because an essay is of a quality far higher than I would have expected) I reserve the right to conduct an oral examination of that student, in the presence of an academic colleague. But these methods of detection are not fool-proof.

At the beginning of April a blogger, referring to Rabbi Bernheim's 2011 book Forty Jewish Meditations, accused him of having reproduced, without attribution, a statement made by the philosopher Jean-François Lyotard and published in 1996. Then another blogger declared that Bernheim had also plagiarised text in a book he had published in 2002. Worse still, accusations surfaced that a pamphlet authored by Bernheim last October - in which he declaimed against the French government's intention to legalise gay marriage - had also contained instances of plagiarism. And a French magazine revealed that he had not actually earned (by passing an exam known as the aggregation) the title of professor that publicity for his books reportedly claimed he possessed.

Bernheim appears to have admitted his guilt

By resigning, Bernheim appears to have acknowledged his guilt. I am certainly not going to defend him. But I am going to place before you certain facts related to another theologian, and then ask you to ask yourselves why one serial plagiarist has been exposed and disgraced, while another has been - to all intents - canonised.

That theologian is Martin Luther King Jr, the celebrated civil rights activist who was infamously assassinated in Memphis, Tennessee, 45 years ago this month.

King, in whose honour a national holiday is celebrated in the US, was not just a plagiarist. He was an habitual plagiarist. His Boston University PhD, awarded in 1955, contained numerous plagiarised passages - a conclusion endorsed by a board of inquiry established by that university some years later. To those of you interested in learning more about this I recommend Plagiarism & The Culture War, a meticulous exposé of King by Theodore Pappas from 1994. Pappas reproduces, side-by-side, passages from King's PhD and from the work of a fellow Boston University student, whose doctoral dissertation had been approved in 1952.

The evidence is irrefutable. Armed with his dishonestly earned doctorate, King went on to publish articles and books that incorporated - without attribution - passages lifted from the works of others. His celebrated 1963 oration ("I have a dream… "), which has been described as the "defining moment" of the American civil rights movement, climaxed with the invocation "let freedom ring". King failed to acknowledge that these very words had been used by another black preacher - Archibald Carey - at the Republican National Convention 11 years earlier.

Boston University has obstinately refused to revoke King's doctorate, while his supporters have actually sought to explain - and even to justify - his acts of intellectual dishonesty. Bernheim, whom Nicolas Sarkozy awarded the Legion of Honour in 2009, has been banished, in disgrace. Is this - I wonder - because King was the hero of the left, while Bernheim was an icon of the right?