… is from page 210 of the 1997 Johns Hopkins University Press edition of H.L. Mencken’s indispensable 1956 collection, Minority Report :
The divisions between nations are not natural, and the common people seldom of their own motion cherish national animosities. They are promoted by professional politicians, the eternal enemies of human peace and security. It is always to the interest of such politicians to arouse fears. They make their living doing so, and then promising to get rid of the bugaboo by quack devices. One of the worst of these quack devices is the customs barrier…. What is universally good should be obtainable everywhere, and at substantially the same price.