Another part of Donald Trump’s interview with Chris Matthews is now causing heartburn in various locales — namely his refusal to rule out the use of nuclear weapons in the Middle East and Europe. Matthews couldn’t understand why Trump declined to simply say “no nuclear weapons.” In this, actually, Trump isn’t actually wrong. (There’s always a first time! ) Here’s Matthews:

OK. The trouble is, when you said that, the whole world heard it. David Cameron in Britain heard it. The Japanese, where we bombed them in ’45, heard it. They’re hearing a guy running for president of the United States talking of maybe using nuclear weapons. Nobody wants to hear that about an American president.

Throughout the Cold War, NATO never said it would not use nuclear weapons in the event of a Soviet invasion of Western Europe. NATO’s possible response was kept vague, but the threat was implicit. That’s why we placed intermediate-range missiles in Europe during the Reagan administration. That’s why we declined to sign on to the “nuclear freeze” movement, and so on. Without the threat of nuclear retaliation, we would have had to station many more troops and conventional assets in Germany.

No, the problem is not refusing to rule out the use of nuclear weapons, the problem is the man who’s saying it. Trump has showcased his appalling ignorance about the basics of American government, finance, history, constitutional order, and foreign policy throughout this campaign. Hugh Hewitt’s question about the nuclear triad produced a response that revealed Trump’s complete ignorance of this most basic fact about our deterrent posture. And for the last week or so, he’s been letting fly with barstool suggestions like sinking NATO, abandoning our alliances with Japan and Korea unless they pay up, and encouraging other nations to obtain their own nuclear weapons rather than relying on the American “nuclear umbrella,” which has been a pillar of U.S. foreign policy since the end of World War II. The dangerous and alarming thing is that an overgrown adolescent who admires dictators, condones violence of many kinds, and doesn’t know the Quds Force from the Kurds is a leading Republican candidate for president. That’s the thing that has the world looking on in horror.