It's not censorship, it's just a form of "truth in labeling".

If you're a vegetarian or a strict Jew or Muslim, you want to have food
labeled accurately so you won't accidentally open a can that causes
you to violate your rules or lose your salvation.  Thus food makers are careful
to put Kosher, Halal, and lists of ingredients on cans, in order to give
people something they can buy without fear.

Same with nudity.  Some folks have religious, legal or personal
restrictions on what they can view.  Without the labels, these folks
would have to avoid "shopping" for art entirely.

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