As for violence, where would art and literature be without it? The Book of Genesis could not go more than three chapters without its first murder. Bodies litter the stage in Shakespeare’s tragedies. Grimm fairy tales are grim indeed. In the American Film Institute’s lineup of the 100 greatest American movies of all time, at least 60 contain one form of brutality or another, much of it exceedingly bloody.

One film classic from 1949, which did not make the institute’s list, offers the proposition that violence and cultural achievement often go hand in hand. “You know what the fellow said,” a character in “The Third Man” says. “In Italy for 30 years under the Borgias, they had warfare, terror, murder and bloodshed, but they produced Michelangelo, Leonardo da Vinci and the Renaissance. In Switzerland, they had brotherly love. They had 500 years of democracy and peace. And what did that produce? The cuckoo clock.”

The advent of warning labels has hardly ended the artistic exploration of sex and violence. Notwithstanding Mr. Zappa’s dire forecasts, government repression does not reign. The last time anyone looked, songs were still being recorded and teenagers were still listening. An argument could even be made that these labels sometimes have an effect other than the intended one, by pointing teenagers, who practically live to upset their elders, in the direction of the forbidden fruit.

And the labels keep coming. The latest, as Retro Report notes, are “trigger warnings” that have been proposed on some college campuses, to alert students to curriculum material that may upset them or possibly cause post-traumatic reactions in, say, rape victims or combat veterans. Works suggested for such advisories have included “The Great Gatsby” (misogyny), “The Merchant of Venice” (anti-Semitism) and “Mrs. Dalloway” (suicide). Are these alerts a reasonable way to shield the more vulnerable from harm, as proponents assert? Or are they, as critics fire back, a misguided notion that infantilizes students who would be better served by dealing directly with life’s harsher realities?

When it comes to warnings, consistency is not always a helpmate. Susan Baker, for instance, told Retro Report that she still believes in the importance of labels for explicit music, but that she was skeptical about classroom trigger warnings. Whether one is right or left politically, much seems to depend on the target — on, if you will, whose ox is Gored.