Last Saturday’s stabbing of two Museum of Modern Art clerks was distressing, but it wasn’t shocking. Most of us know by now that violence has soared in New York City. What is shocking to the few remaining naïve urban innocents who think that Gotham doesn’t need proactive law enforcement is the revelation of an open secret: MoMA, a supposedly liberal arts institution, practices broken-windows policing.

Gary Cabana, the stabbings suspect, wasn’t a stranger to the gallery. But after he behaved in a disruptive manner twice this year, the museum banished him, revoking his membership. 

Cabana’s earlier disorderly conduct didn’t rise to felony level. Yet MoMA banned him anyway. Why?

First, nobody wants to be around a persistently disruptive patron. Unpredictable, uncivil behavior makes everyone miserable.  

Second, disorderly behavior often escalates to violence. In this case, it obviously did.  

In exiling Cabana from its premises before he returned to allegedly stab two workers, MoMA didn’t bother with all the postmodern excuses for disorderly behavior.  

Did mental illness drive Cabana’s earlier disruptions? Probably, and that was likely apparent during those incidents. 

MoMA didn’t worry itself overmuch about the “help he needs,” though. It sacrificed the privilege of one disturbed person to safeguard the environment for everybody else. (You can bet museum officials are glad that Cabana doesn’t appear to be black.)  

After the stabbings, when the museum thought Cabana was lurking on the premises, it invited heavily armed police to swarm the place, even though there was a risk they would shoot and kill him. 

MoMA bills itself as “inclusive” and “tolerant,” a place where “diverse” voices — even “political positions” — are “welcome.” Notice the museum doesn’t say “all are welcome.” They’re not. 

All this “inclusion” and “tolerance” (and everyone’s pleasant, enriching day) depends on a foundation of rules to maintain order — backed, in the end, by the armed government.

MoMA also keeps protesters out. Last year, it met a planned demonstration within the museum with armed police and shuttered doors.  

As with Cabana’s escalating behavior, museum officials seem to have absorbed the fact that “peaceful protests” over the past two years have often grown destructive.  

This all makes sense. You can’t run a large institution in an environment of chaos. 

In this, MoMA is far less exclusive than many other elite institutions. If you have a municipal IDNYC card, you can get a free one-year membership (only once every five years).  

The private universities that boast of their “safe spaces,” by contrast, maintain their “best colleges” rankings by keeping 90%-plus of the people who would like to go to school there out. 

Even as MoMA sticks to its broken-windows-policing policy, though, New York City tolerates all sorts of chaos and disorder.  

Mayor Eric Adams is trying to fix that. But he’s still hemmed in by Democratic state legislative leaders who resist any attempt at bail reform for big crimes and by district attorneys (particularly Manhattan’s Alvin Bragg) and judges who resist any punishment for small crimes.  

The results of this approach were on display again last week. Washington Square Park is supposed to close at midnight, a perfectly reasonable rule that’s gone unenforced since summer 2020. Neighborhood residents tired of all-night partying there over the past two years are dismissed as racist NIMBYs.

A teenager was stabbed in the head there Friday by thieves after his marijuana — at 2:30 a.m. 

Funny how that works. If the city had enforced the small rule — the closing time — it could have averted the violent assault.  

MoMA doesn’t let you jump over the metaphorical turnstile if you don’t have $25 (you have to apply in person for your free one-year membership under IDNYC).

But the state-run Metropolitan Transportation Authority is forced to ignore tens of thousands of such chronic trespassers every day.  

The MTA can’t ban people after they’ve been disorderly. Even if police arrest suspects on “low-level” charges — increasingly rare — chronic lawbreakers face no deterrence. The disorderly, and even people accused of serious assaults, return, again and again, to harass and menace paying customers.  

Drugstores and supermarkets summon the police to arrest a shoplifter — only to see the thief return.  

It may be time to take some enlightened inspiration from the liberal arts world: If you can’t behave, you will face the consequences.

Nicole Gelinas is a contributing editor to the Manhattan Institute’s City Journal.