Ramesh – I agree that most libertarians will have no problem endorsing gay marriage. But for many of them, that strikes me as further evidence that the much-vaunted “consistency” of libertarianism can be — and often is — turned off at will. I don’t think Smith’s is a silver-bullet-argument by any stretch, but it’s hard to imagine many prominent libertarians coming out in principle against gay marriage even if in practice they see nothing wrong with it.