Simon accuses Nick Robinson of under-emphasizing "the conflict between scientific and acrobatic journalism" - that journalism which seeks the truth and that which is "always looking for balance." This raises the question: why would Mr Robinson (and much of the BBC) have such a blindspot.

I suspect it's partly because of a longstanding assumption among much of the Establishment, of which the BBC is part. This assumption is a form of the Wykehamist fallacy, the belief that members of that Establishment are jolly good chaps, usually because they went to the right schools and universities.

If you believe this, you'll believe that disagreements are between decent honest men (usually men) who happen to have a partial perspective. Given this assumption, it follows that the truth is likely to be somewhere in between. There will then be no great tension between balance and the search for truth.

We don't have to look far for examples of the Wykehamist fallacy. We've seen it for example in the treatment of Boris Johnson as a loveable eccentric rather what he is, a dangerous idiot: it might be no accident that the only BBC interviewer to expose him is a lorry-driver's son from Dundee and not the standard simpering deferential posh journo.

In truth, of course, the Wykehamist fallacy is an ancient one. Adam Smith was describing something like it when he wrote:

We frequently see the respectful attentions of the world more strongly directed towards the rich and the great, than towards the wise and the virtuous. We see frequently the vices and follies of the powerful much less despised than the poverty and weakness of the innocent. (Theory of Moral Sentiments, I.III.29)

Nor, of course, is it confined to the BBC. Janan Ganesh writes that the British political system "trusts the life of the nation to a few offices and prays for worthy occupants." This is because there's been an assumption that those occupants would indeed be jolly good chaps.

This is also why MPs day-to-day behaviour went largely unpoliced at least before the expenses affair; why the top professions were traditionally self-regulated; why there's been little restraint upon chief executives; and why there was until quite recently little serious effort to stamp out large scale tax avoidance.

All these are the results of the Wykehamist fallacy - the belief that jolly good chaps can be trusted to do the decent thing.

But they can't. MPs' sexual harassment, legalized theft by bankers and bosses, and tax-dodging all testify to the fact that the JGCs are morally indistinguishable from the people on the Jeremy Kyle show: they just have better teeth.

Which brings me back to Simon's point. When one side of a debate tells a bare-faced lie - about that £350m for the NHS for example - a conflict between scientific and acrobatic journalism does arise. But you'll not see it if your presumption is that people will at least try to tell the truth if they went to good schools, as Johnson, Farage and Banks did.

Now, I have an open mind on the question of whether the Wykehamist fallacy was always wrong or whether it's become more so in recent years, and if so why. It does, however, seem to be the case that the BBC's efforts to strain too hard for "balance" in one sense reveals that it is, in another way, profoundly unbalanced. And in a class-divided society it could not be otherwise.