Nebraska Senator Ben Sasse appeared on HBO’s “Real Time with Bill Maher” to promote his new book, “The Vanishing American Adult: Our Coming of Age Crisis — And How To Build a Culture of Self Reliance.”

Thanks to Bill Maher’s infamous and irreverent mouth, a routine publicity spot turned into a media storm.

Now Maher has discovered that even a rich, left-wing provocateur has lines he can’t cross. And using the N-word is one of them.

Whether he will pay a price for his casual exploitation of the pain of others remains to be seen.

Maher did Sen. Sasse a kind of favor. His behavior was advertisement for the relevance of Sasse’s book.

Sasse discusses in this book what he sees as a trend in America toward “perpetual adolescence” — a deferral of the transition from child to adult.

He is not talking about biological adulthood. He is talking about cultural adulthood.

It’s about taking responsibility for one’s life and, in an even broader sense, for the challenge of living.

We come into this world as egoists. Everything revolves around us. Growing up involves discovering that the world is about more than me, that there are others, and that we are all part of something greater than ourselves.

But this is really exactly the opposite frame of mind that our society today supports.

Everything is about me — my wants, my claims, my rights.

A Gallup poll from last month bears the headline “Americans Hold Record Liberal Views On Most Moral Issues.”

Positive responses are at record highs for the moral acceptability of birth control (91 percent), divorce (73 percent), sex between an unmarried man and woman (69 percent), homosexual relations (63 percent), out-of-wedlock birth (62 percent), abortion (43 percent), and pornography (36 percent).

Despite the overwhelming evidence correlating traditional family life with personal health and prosperity, Americans are increasingly casting aside this vital social institution. Why? Because along with it comes responsibility, caring about others as well as oneself, and caring about the future as well as the present. Taking on the responsibility of marriage and family means transitioning to becoming an adult.

This transition also means appreciating and recognizing that there is knowledge I do not have, and that it is important to learn. This builds humility rather than arrogance.

In a society without an appreciation for lifelong learning, where young people arrive at universities feeling they already have enough wisdom, media is going to be about entertainment, not knowledge.

So our media stars are provocateurs such as Maher, whose objective is to violate sensibilities, because this builds audience. He doesn’t care about knowledge. He also doesn’t care about respect, and what was once taught as the Golden Rule — to treat others as you wish to be treated. This is adult behavior.

So, Bill Maher helped Ben Sasse make his case about “The Vanishing American Adult” by showing how he makes a handsome living in a society that rewards perpetual adolescence.

Of course, Bill Maher is far from alone. Increasingly, all our media is about provocation rather than knowledge.

Meanwhile, Sen. Sasse has an important message for the nation. If we want a future, we need to grow up