In the penultimate chapter of his book The Better Angels of Our Nature: Why Violence Has Declined, Steven Pinker attempts to bring together the tenuous linking of increased free market libertarianism and increased peace:
"To think like an economist is to accept the theory of gentle commerce from classical liberalism, which touts the positive-sum payoffs of exchange and its knock-on benefit of expansive networks of cooperation. That sets it in opposition to populist, nationalist, and communist mindsets that see the world's wealth as zero-sum and infer that the enrichment of one group must come at the expense of another."
In my case, he's pushing at an already open door with a comment like that, but then I'm not one of the people that needs convincing - I mean, as I've blogged about a couple of times now, it's pretty evident if you look the nations that most espouse economic freedom, democracy and liberalism, they are pretty much always the most peaceable countries too.
As well as the obvious point - that free trade is underwritten by co-operation, empathy, and a stable rule of law that protects individual rights - what Pinker means by 'thinking like an economist' is probably that people well versed in economics are not so heavily sullied with the divisional myths that pervade the left; like for example, class stratification, wanting to forcibly confiscate wealth from higher earners (the higher the taxes the better), enviously resenting those who are successful, failing to note when value is being created, falling for the fixed pie fallacy and feeling a false sense of entitlement for what others have acquired, thinking that the economy is zero-sum, lamenting when other more competitive industries prove to be more efficient than industries in their own country, and treating others as less important if they happen to belong to a country outside of their own geographical borders.
The link between peace and the free market is tenuous, but that's only because the entirety of our global interactions, past and present, amounts to a vast nexus of tenuous and complex correlatives. And it's not the first time that we've talked about it.