Sex, drugs and some kid blasting into a microphone: It’s still the most shocking, most fun combination of anything in the world, still the stuff that blasts each generation out of childhood into the thrill of youth. Kneecap, both the Irish-language rap band and the film in which the three “low-life scum” band members play themselves, have managed to delight vast crowds — including the ones that gave the film the Next Audience Award at Sundance — while making culture-war enemies all the way to the top echelons of the British government. Which is entirely as it should be.

First, a word about those cultural enemies. Kneecap rap in Gaelic, once banned from classrooms in Northern Ireland — the six counties of Ireland that remain under British governance — and only recently (and very controversially) given the status of an official language of the land. Naoise Ó Caireallain, one of the two boyhood friends who start Kneecap,...