RALEIGH — On April 30, a mob of pro-Hamas protestors defaced public property at the University of North Carolina in Chapel Hill and yanked down, for a brief time, the American flag fluttering over a prominent part of the campus called Polk Place.

Then-interim leader Lee Roberts responded with firmness and resolve. He is now the chancellor of UNC-Chapel Hill. A group of fraternity brothers helped defend and restore the flag to its rightful place. They became national heroes.

Advancing the Palestinian cause not an inch with their violent and disorderly conduct last spring, the pro-Hamas protestors — yes, they quite explicitly advocate terrorism and the removal of Jews from the Levant, not true “peace” or “justice” — decided to try the same tactic a second time. On September 19, they formed another mob and marched across the campus, screaming at the top of their lungs and spray-painting the likes of “F—k UNC” and “Death to US” on campus buildings.

Then, of course, they pulled down the American flag that flies over Chapel Hill’s ROTC building. By the time police arrived and restored the flag, most of the protestors had fled.

As I have previously argued, students and non-students alike enjoy the right to express themselves freely on university campuses. They can write what they want. They can say what they want. They cannot, however, commandeer public property without permission. They cannot disrupt classes or otherwise impede the normal functions of the university. And as no one truly committed to peace and the rule of law can plausibly deny, protestors have no right to deface or remove public property, no matter how passionately they may feel about the cause they espouse.

Yes, the graffiti was quickly painted over and the flag raised above the ROTC building. But university employees and law enforcement have better things to do with their time. More importantly, those who work, study, or live on the UNC-Chapel Hill campus deserve to do so in peace and security.

Any students or employees participating in such unlawful protests ought to be suspended. Second offenses ought to result in expulsion or termination. Occupying or defacing public property is not the exercise of free speech. It is the commission of a crime.

I admit that I’d hoped activist groups and their donors had learned a lesson from the debacle last spring. After dozens of violent protests on campuses across the country — many that featured chilling episodes of Jewish students being threatened, chased, or assaulted — it was the defenders of Israel, America, and the rule of law who prevailed in the court of public opinion, not the apologists for Hamas.

If the goal really was to increase public awareness of the plight of innocent Palestinians caught in the crossfire between the Israeli armed forces and their terrorist adversaries, last spring’s spate of campus clashes was obviously counterproductive.

You can’t persuade students to adopt your position by interfering with their studies and threatening their classmates. You can’t persuade university leaders to redirect their investment dollars by disrespecting and ridiculing them. And you certainly can’t persuade Americans to shift their allegiances by insulting their country and their flag.

Matthew Trott, who heads the university’s College Republicans chapter, put the matter plainly. “Peaceful protests are a hallmark of our society and can encourage and facilitate positive discourse,” he told Carolina Journal, “but it is unfortunate that the protesters chose to vandalize public property and desecrate the American flag instead of using a more positive method for dialogue.”

In today’s overly polarized, hyper-cyber mode of political discourse, calmness and respect are often mocked as quaint niceties, as weakness. Nothing could be further from the truth. It takes strength to follow the rules, to restrain one’s impulses, and to listen carefully to the views of others so as to better understand them — and your own.

One purpose of a university education is to inculcate such virtues in the next generation. Strong leadership now will produce a stronger country tomorrow.

John Hood is a John Locke Foundation board member. His latest books, Mountain Folk and Forest Folk, combine epic fantasy with early American history (FolkloreCycle.com).