When Kermit the Frog found El Sleezo Cafe, a stereotypically Mexican joint in 1979’s “The Muppet Movie,” he nervously muttered, “Foreign food … but a man’s gotta eat.” Never mind that the house special turned out to be frog’s legs — such a scene today would go straight to the cutting-room floor and the creators exiled to Cancelville. Once upon a time, it was permissible to make light-hearted fun of cuisines that were unfamiliar or exotic to film audiences. But in today’s unforgiving and witless world of Indigenous-Cuisine Purity, good-natured jokes are strictly verboten. Worse, just about any dish not...