1. Free trade, in its true, complete, and intellectually coherent form, is not limited to the free movement of goods, but includes the free movement of capital and labor as well. (The “invisible judicial line” doesn’t magically become visible when because human bodies are involved.)
2. The difference between domestic economies and the global international economy is not trivial, but is substantive, material, and based on significant genetic, cultural, traditional, and legal differences between various self-identified peoples.
3. Free trade is totally incompatible with national sovereignty, democracy, and self-determination, as well as the existence of independent nation-states with the right and ability to set their own laws according to the preferences of their residents.
4. Therefore, free trade must be opposed by every sovereign, democratic, or self-determined people, be they American, Chinese, German, or Zambian, who wish to preserve themselves as a free and distinct nation possessed of its own culture, traditions, and laws.
To illustrate why nationalists may also oppose open-borders free trade on grounds of political economy, it is only necessary to say that a man who works hard to support his wife and children may not work so fruitfully living independently in an atomised culture of strangers. This, we can observe with a perfunctory glance at employment levels for young people. By extension, if we consider races to be subpopulations of disproportionate interbreeding, then regardless of necessity (or other confounds) a man will also work harder when he lives among his own kind. And more happily, by my observation.
There is also a fundamental flaw in Ricardo’s theory, which is to assume that all men are productive. That is, Bob can produce 8 of A or 5 of B in a man-hour, while Frank can produce 6 of A or 2 of B in a man-hour. If you have worked a day in your life, you have probably met someone this does not describe, who could not produce an A if their life depended on it and would produce negative quantities of B if they tried. Such economic parasites exist within the population in varying proportions either through hook, crook, charity, deceit, or dumb luck. Furthermore, many men are slaves at heart who would starve under a libertarian system, but would be passably productive through fear of the lash. Classical economics is naive in these regards, and therefore untrustworthy in matters discussed by serious thinkers.
Economics is to public policy as chemistry is to medicine: a useful set of mental models, which in any case may or may not describe the primary factors in a particular experiment. That is why I suggest, as ever, that we prefer conservatism to achieve stability, and afterward prefer less risky and more predictable social experiments than, for example, the East has done by transplanting Western culture.
(But then, maybe this is because I view induction as superior to deduction, in that it is more useful and more general: we can induce the truth of deduction, but we have yet to deduce the truth of induction.)