"I have endeavoured to shew, even upon the principles of the commercial system, how unnecessary it is to lay extraordinary restraints upon the importation of goods from those countries with which the balance of trade is supposed to be disadvantageous.
Nothing, however, can be more absurd than this whole doctrine of the balance of trade, upon which, not only these restraints, but almost all the other regulations of commerce are founded. When two places trade with one another, this doctrine supposes that, if the balance be even, neither of them either loses or gains; but if it leans in any degree to one side, that one of them loses and the other gains in proportion to its declension from the exact equilibrium. Both suppositions are false. A trade which is forced by means of bounties and monopolies may be and commonly is disadvantageous to the country in whose favour it is meant to be established, as I shall endeavour to show hereafter. But that trade which, without force or constraint, is naturally and regularly carried on between any two places is always advantageous, though not always equally so, to both...
By such maxims as these, however, nations have been taught that their interest consisted in beggaring all their neighbours. Each nation has been made to look with an invidious eye upon the prosperity of all the nations with which it trades, and to consider their gain as its own loss. Commerce, which ought naturally to be, among nations, as among individuals, a bond of union and friendship, has become the most fertile source of discord and animosity. The capricious ambition of kings and ministers has not, during the present and the preceding century, been more fatal to the repose of Europe than the impertinent jealousy of merchants and manufacturers. The violence and injustice of the rulers of mankind is an ancient evil, for which, I am afraid, the nature of human affairs can scarce admit of a remedy. But the mean rapacity, the monopolizing spirit of merchants and manufacturers, who neither are, nor ought to be, the rulers of mankind, though it cannot perhaps be corrected may very easily be prevented from disturbing the tranquillity of anybody but themselves.Adam Smith destroyed the argument in favor of economic protectionism more than 200 years ago in his most famous book, The Wealth of Nations.
That it was the spirit of monopoly which originally both invented and propagated this doctrine cannot be doubted; and they who first taught it were by no means such fools as they who believed it. In every country it always is and must be the interest of the great body of the people to buy whatever they want of those who sell it cheapest. The proposition is so very manifest that it seems ridiculous to take any pains to prove it; nor could it ever have been called in question had not the interested sophistry of merchants and manufacturers confounded the common sense of mankind. Their interest is, in this respect, directly opposite to that of the great body of the people. As it is the interest of the freemen of a corporation to hinder the rest of the inhabitants from employing any workmen but themselves, so it is the interest of the merchants and manufacturers of every country to secure to themselves the monopoly of the home market. Hence in Great Britain, and in most other European countries, the extraordinary duties upon almost all goods imported by alien merchants. Hence the high duties and prohibitions upon all those foreign manufactures which can come into competition with our own. Hence, too, the extraordinary restraints upon the importation of almost all sorts of goods from those countries with which the balance of trade is supposed to be disadvantageous; that is, from those against whom national animosity happens to be most violently inflamed.
The wealth of a neighbouring nation, however, though dangerous in war and politics, is certainly advantageous in trade. In a state of hostility it may enable our enemies to maintain fleets and armies superior to our own; but in a state of peace and commerce it must likewise enable them to exchange with us to a greater value, and to afford a better market, either for the immediate produce of our own industry, or for whatever is purchased with that produce. As a rich man is likely to be a better customer to the industrious people in his neighbourhood than a poor, so is likewise a rich nation."
So how come economic illiterates from Bernie Sanders to Donald Trump continue to argue for protectionist policies 200 years later?
Oh, yeah! That's right! Because human greed and ignorance continues to surpass human knowledge!