And there it is today in the Panama Papers tax row. I’ve said it myself about David Cameron’s explanations. He has obeyed the law. He has done nothing wrong. So that’s okay, then, is it? Janan Ganesh writing in the FT today makes that case. Moral exhortation is nonsense, he says, and the “woolly-minded notion of fairness is no way to run a tax system.” I see what he means. But…