Republican vice presidential nominee J.D. Vance has been in the news for an old clip of him talking about how the tax code should punish adults without kids. While Vance’s proposal probably aims to address demographic concerns, it represents a misguided approach that contradicts fundamental principles of economic freedom and fairness. And you know what? That’s precisely what our tax code already does, in this case and many others. Using the tax code to “reward” parents and “punish” nonparents is at odds with the idea of a neutral, efficient tax system. In an ideal and fair world, the tax base …