The chants and signs in support of Hamas are becoming increasingly dangerous.
They go well beyond supporting the people in Gaza, or even opposing Israel’s right to exist.
Some now defend the murders and rapes committed by Hamas and demand even more violence against Israeli citizens.
Protesters chant, “We are Hamas,” “We love Hamas rockets,” ”Burn Tel Aviv to the ground” and “10,000 repetitions of October 7th.”
A leader of the Columbia rioters recently said “Zionists don’t deserve to live” and that he feels “very comfortable calling for these people to die” (though he later apologized).
If Hamas is not defeated in Gaza, it is likely that its terrorism will extend beyond the Middle East.
Already Hamas terrorist cells have been identified in several European cities.
It is almost certain that Hamas operatives are planning terrorist attacks in the United States as well.
It is not a bridge too far to believe that radicals who claim to be in Hamas, love their rockets and call for the death of Israelis and Jews might take the next step and help Hamas operatives engage in terrorism against US targets.
They could be recruited to help purchase weapons, identify targets and even plant bombs.
Something similar happened in the late 1960s and early 1970s when American supporters of terrorism became terrorists themselves, including students, professors and university graduates.
They planted bombs, tried to blow up army bases and recruitment centers and murdered police officers and armed guards.
For them, as with today’s Hamas supporters, “any means possible” justifies their revolutionary ends.
Hamas will do the same if given the opportunity in this country.
The line between advocacy, incitement and actual violence is not always an easy one to draw, though the First Amendment demands that we do so.
But common sense also demands we be on guard, lest these lines be crossed invisibly or quietly, as terrorists often do.
We may not be able to arrest and prosecute people who advocate murder, rape and rocket attacks, but we surely have the power, under our constitution, to be concerned and to take constitutionally permissible precautions against the possibility that radicals who advocate violence may well engage in it in the not-too-distant future.
During the Vietnam War protests, law-enforcement authorities were caught off guard.
They did not believe college-educated protesters from good families would turn into terrorists.
But they did, and people died.
Some of the terrorists went to prison. Others did not.
Some who went to prison for murder, like Kathy Boudin, were actually hired after their release by universities like Columbia to teach students.
Others were befriended by the likes of Barack Obama.
The terrorists of the late 1960s and early 1970s were glorified by the media — and continue to be so in films and books.
We must never glorify terrorists, for starters. Rather, we must do everything in our power to prevent violent and hateful protesters from turning into murderous terrorists.
This must all be done consistent with the First Amendment.
But we must be prepared for actual violence from those who currently advocate violence.
Certainly, our law enforcement and intelligence agencies must remain on alert, monitoring social media channels and, perhaps, looking for links between, say, protesters who commit crimes and known terror groups and individuals.
Track funding sources, too. The lights are flashing; connect the dots.
Most of those who today support and admire Hamas will not cross the line from advocacy to terrorism, but some likely will.
It is difficult, if not impossible, to distinguish the less dangerous former from the more dangerous latter, but we must try, within the constraints of the Constitution.
No democracy can ignore the presence of a dangerous “fifth column” aiming to do us harm at the behest of enemies like Hamas.
When you watch these agitators call for “Death to America” and praise Hamas rockets, remember: You may be their next target.
As the late Elie Wiesel reminded us, “It may start with the Jews, but it rarely ends with Jews.”
Alan Dershowitz is a professor emeritus at Harvard Law School and author of “War Against the Jews: How to End Hamas Barbarism.” Andrew Stein, a Democrat, served as New York City Council president, 1986-94.