As I read the First Amendment, it was designed to keep the state and the hands of all state officials off the printing presses of America and off the distribution systems for all printed literature. I think it would require a constitutional amendment to achieve that result. If there were a constitutional amendment, perhaps the people of the country would come up with some national board of censorship. Censors are, of course, propelled by their own neuroses. That is why a universally accepted definition of obscenity is impossible.
Any definition is indeed highly subjective, turning on the neurosis of the censor.
Those who have a deep-seated, subconscious conflict may well become either great crusaders against a particular kind of literature or avid customers of it. That, of course, is the danger of letting any group of citizens be the judges of what other people, young or old, should read. Those would be issues to be canvassed and debated in case of a constitutional amendment creating a regime of censorship in the country.