America followed its values and the better instincts of its nature, entered WWII and ensured that Europe and the West would not descend into the darkness. To the French and so many Europeans, we were the good guys fighting for the cause of good. Mr. Trump seems to think differently.

Earlier this summer, my wife and I took a brief detour between business obligations elsewhere in Europe to visit Southern France. Although this region is much hyped and quite crowded with tourists during the summer months, one can still enjoy the its unique beauty and rich culture away from the better-known gathering places along the Mediterranean coast.

So we parked ourselves in a small French town some 30 miles inland and comparatively empty of crowds. It was as delightful as advertised. But we were treated to something special and, for Americans, most heartwarming.

One evening in our B&B, we heard American music coming from the town’s main street only a couple of blocks away. The B&B owner informed us it was part of the region’s celebration of “La Liberation.” Not quite sure which liberation she may have been referring to, we were attracted by the music, from 1940s boogie and jazz to 1960s rock and roll to more modern pop, as well as French music from the same periods.

Upon arriving at the event, we caught sight of a large, vintage World War II-era U.S. Army truck whose cargo bay held the DJ and his sound equipment. Nearby, we spotted other trucks, jeeps, an ambulance and several motorcycles, all U.S. Army WWII leftovers. Dancing nearby were dozens of young and middle-aged men wearing U.S. Army WWII uniforms complete with unit insignias and Americans flags sewn on their sleeves. Many of the women with whom they danced were decked out in the fashions of the 1940s.

The date was Aug. 15, the 73rd anniversary of Operation Dragoon, the Allied invasion and liberation of Southern France along the now famed Cote d’Azur of Provence. From Marseilles in the west to St. Rafael (near Cannes) in the east, including today’s go-to place for the rich and famous, St. Tropez, tens of thousands of U.S forces joined by Free French, French Resistance and other allied forces — more than 150,000 in all — stormed the beaches and cliffs of this iconic coastline and drove Nazi forces back into central France. Ten weeks before, the Allies had launched a more massive invasion at Normandy.

That evening, the French remembered their liberation from the tyranny of the much-despised Nazi occupiers by forces coming from thousands of miles away. As we later learned, French citizens participate in re-enactments of World War II much as Americans do for the American Revolution and Civil War. The Aug. 15 tribute is second only to the Normandy commemoration. Both the French and the hundreds of thousands of Americans who died to liberate France are still fondly remembered by young and old.

It was an unexpected, uplifting experience for us, and we were elated to see America remembered in such a gratifying manner. But our elation was quickly dispelled. My wife glanced at her phone and saw a depressing media alert reporting that our president had for a second time equated the neo-Nazis, KKK and white supremacists at Charlottesville with the counterprotesters.

The president of the nation most responsible for defeating and eliminating Nazis, the very apotheosis of hatred and intolerance in the mid-20th century, was now equating their resurrected remnant to those protesting racism, anti-Semitism and bigotry. His remarks were a betrayal to all that Americans believe and, in the case of World War II, all those who fought, sacrificed and died in that noble cause.

In 1944, Americans were the quintessential good guys, fighting on foreign shores to defeat enemies who seemed to personify evil. The Nazis sought to assert domination of one race over all others, eradicate one entire group of people, and ultimately dehumanize the rest. For all its faults then and now, America followed its values and the better instincts of its nature, entered that war and ensured that Europe and the West would not descend into the darkness. To the French and so many Europeans, we were the good guys fighting for the cause of good.

As a veteran and former career diplomat, I struggle to understand not just why the so-called alt-right identifies with one of history’s most reviled and murderous movements but also how our president could tolerate them, as he effectively did when putting them on the same level as those protesting the alt-right in Charlottesville.

If he truly believes such equality exists, I suggest he speak with Holocaust survivors or the children of those African-Americans who suffered during the Jim Crow era in this country or, next Aug. 15, with the good people of Southern France. For them, and for most conscientious Americans, there can never be such equivalence.

Only vigorous, unequivocal condemnation will suffice, Mr. President.