BBC1's The Last Post depicts a group of mostly decent men upholding what many of you regard as an unjust system, of colonial rule. This illustrates an important and under-appreciated point - that the justice or not of social systems is not reducible to, or wholly explicable by, the character of its actors. Social structures are emergent. Or to put the point more trivially obviously, good men can do bad things, and bad ones good things.

To take just two of countless historical examples, Lyndon Johnson did more than most men to advance the cause of racial equality, despite using language that would today disqualify him from politics. And Otto von Bismarck did not create one of Europe's first welfare states because he was a soft-hearted liberal*.

The classical economists saw this point clearly. Smith famously wrote that "it is not from the benevolence of the butcher, the brewer, or the baker, that we expect our dinner, but from their regard to their own interest." And Marx wrote that the quality of working conditions "does not, indeed, depend on the good or ill will of the individual capitalist." Smith thought markets caused greedy men to serve others. Marx thought they caused good men to exploit others. But both agreed that market outcomes weren't reducible to individuals' characters.

Instead, what matters are incentives and selection mechanisms. This is true not just of markets, but of organizations and political structures. If we have the right such mechanisms, then bad men can do good things. If we have the wrong ones, good ones will do bad things.

Which brings me to two more recent developments. Simon points out that Article 50 negotiations are going badly in part because the media did not facilitate a rational assessment of the UK's bargaining position. This is an example of how political structures select (or at least filter) against good policy-making.

And then we have the fuss over Jared O'Mara. Phil makes a good point when he notes that words are not the only form of sexism and that in their actions the Tories are structurally sexist:

Who do they think suffer disproportionately from their Parliamentary votes to cut to social security, their cuts to the NHS, their real terms cuts to public sector wages?

This would be true even if each individual Tory MP were not personally sexist (which of course isn't the case).

Now, there's a danger here. It's easy for Labour to downplay individual displays of sexism, homophobia or anti-Semitism in the belief that the party is structurally a force for equality. There might be an element of self-regard and wishful thinking here: organized labour has not, historically, been wholly untainted by sexism and racism.

Nevertheless, the point remains. We shouldn't look only at individual politicians' characters but at political structures. Do these promote justice (or efficiency or liberty) or impede it? Do they select for or against good conduct? Ideally, structures would be so selective of good behaviour that individual character would not matter at all.

In this sense, though, we have a paradox. Let's suppose, arguendo, that Tories concerns about O'Mara's language and conduct are sincere and well-founded in fact. What does this tell us about our political structures?

It says that MPs are not selected (by their parties and electorates) to be of good character. And it says that bad character matters because the incentives that MPs face do not rule out future poor conduct.

But this, of course, means that those Tories are making a leftist point - that our social and political structures do not select against sexism and homophobia and might instead help to sustain it. And they might well be right.

* One of the world's first welfare states was created by Genghis Khan, which reinforces my point.