“Jump the shark” is an American pop-culture expression that derives from a 1977 “Happy Days” sitcom episode and describes a moment of decline. At a certain point, a TV show becomes so predictable, empty of ideas and gimmicky that in desperation its writers will try anything — like the character “The Fonz” jumping over a shark on water skis — just to keep on the air.

Contemporary protestors have reached that moment, when demonstrations exist for demonstrations’ sake, without any consistent or coherent agenda of dissent.

At a recent forum on political correctness at the University of Massachusetts, three invited guest speakers were shouted down by protestors in the audience. A video of one shouter went viral. In the manner of a 2-year-old, she threw a loud temper tantrum, interrupting the speakers, screaming obscenities and yelling, “Keep your hate speech off this campus!”

How does one stop “hate speech” by bellowing out four-letter obscenities to disrupt free expression at a university? The childish protestor then proved that she had jumped the shark when she finished by screaming, “Stop treating us like children!”

At an earlier protest at Yale, one particularly emotional student jumped the shark by cursing at a faculty member whose crime was advising students not to overreact to the childish Halloween costumes that other students would be wearing.

Protestors have a right to object to Donald Trump’s various crudities, as long as they do so peacefully and respect the right of free speech. But recently, disrupters at a Trump rally in California likewise jumped the shark when some waved the flag of Mexico or bore placards with slogans such as “Make America Mexico Again.” If the protest was directed against Trump’s pledges to deport undocumented immigrants to Mexico, then it made little sense to celebrate the country to which protestors did not wish immigrants to return, or to suggest that immigrants’ new home should become identical to the old home that they had chosen to leave.

At the University of Missouri last year, protestors demanded concessions from the university. In a public area, assistant communications professor Melissa Click called for “some muscle” to manhandle a student journalist who was trying to photograph a public demonstration. Click might as well have put on water skis and jumped a plastic shark. A right-wing cartoonist could not have dreamed up a sillier scenario, with a faculty member from a university’s communications department trying to have a student reporter physically blocked from covering a news story in a free-speech zone.

Harvard Law School is supposedly as liberal an institution as exists in America. Recently, a Harvard Law student in a public forum asked former Israeli Foreign Minister Tzipi Livni, “How is it that you are so smelly? … It’s regarding your odor — about the odor of Tzipi Livni, very smelly.”

Politically correct Harvard Law Dean Martha Minow offered little more than a broad email condemnation of the incident. In fact, she shielded the identity of the questioner. And just to reiterate its pro-Palestinian credentials, Harvard Law School edited out this anti-Semitic smear from its video of the event.

Last year, someone placed tape over portraits of African-American faculty members in a Harvard Law School building. Minow publicly decried it as a racist act, then later stayed mostly mum about the results of an investigation to find out who was responsible. Yet when Minow recently accepted an award at Brandeis University, a group of student protestors jumped the shark by heckling her for not doing enough to address racism at Harvard Law — even as she was being honored for making “a lasting contribution to racial, ethnic or religious relations.”

Brown University President Christina H. Paxson tried to quiet student protestors by promising to spend $100 million to ensure “a just and inclusive campus.” No matter: The protestors jumped the shark when they derided Brown’s proposed $100 million “Diversity Action and Inclusion Plan” as “insufficient.”

Student debt in America has surpassed $1 trillion. Many graduates did not receive in return an education competitive enough to qualify them for high-paying jobs.

The country owes about $20 trillion in debt. It will soon not be able to meet its pension and Social Security obligations. After slashing the military budget and raising income tax rates, the United States is still running unsustainable annual deficits. The world abroad is becoming dangerously chaotic.

Instead of protesting those existential crises, students cry over Halloween costumes, deride free speech as hate speech, devour their own liberal administrators, and dismiss $100 million payoffs as too little.

Protestors have finally hit rock bottom and jumped the shark. From now on, the same old screaming will be seen mostly as going through the tired motions in lieu of offering coherent ideas.

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