Americans instinctively understand this when our own honor is at stake. The rallying cry during the Barbary Wars, “Millions for defense, but not one cent for tribute,” has almost become part of the national creed. I am no fan of Karl Marx, but he was surely right when he observed that “shame is a kind of anger turned in on itself. And if a whole nation were to feel ashamed it would be like a lion recoiling in order to spring.”

Both the first and second world wars cannot be properly understood without taking seriously the role national honor plays in foreign affairs. Similarly, Vladimir Putin’s constant testing of the West only makes sense when you take into account the despot’s core conviction that the fall of the Soviet Union was a blow to Russian prestige and honor.

Now, I don’t think a war with Mexico is in the cards, even if the Trump administration were to figure out a way to get Mexico to foot the bill for a border wall. But forcing them to pay for it would be a punitive and gratuitous act of humiliation. Expecting a democratically elected president of a sovereign and allied nation to, in effect, grovel to the United States is the equivalent of asking him to drink poison.

Across Mexico, the wall itself is despised as an insult. That’s too bad. And while I don’t think we need some visible-from-space Great Wall of American Greatness stretching from the Atlantic to the Pacific, America has every right to secure its borders in any way it sees fit. But asking Mexico to pay for it literally adds injury to insult. In economic terms there’s little difference between asking them to pay for it and forcing them to build it themselves.