Even before some of them girded themselves for combat with police, donning masks and wielding black shields emblazoned with skeletons, the “Occupy” protesters in Oakland, Calif., engaged in a willfully destructive act.

They shut down the fifth-busiest container port in America. Why would anyone acting in the name of people harmed by the Great Recession interrupt the flow of commerce, especially at a hub employing dockworkers and truckers? It was a symbolic blow against our economic system as such, and by definition a radical act.

It’s become clear during the past few weeks that there is a lawlessness at the heart of Occupy Wall Street. It has created little ungoverned spaces in cities around the country, into which homeless people, addicts and criminals have flowed. It believes that the rules of a fundamentally corrupt system shouldn’t apply to it, and its self-image depends on conflict with the agents of that system, the police.

When asked to do something by an officer of the law, the instinct of most people is to comply, especially if they are violating a rule. The instinct of many of the Occupy protesters is to resist, then inflate their arrests or clashes with the police into a monumental struggle with the forces of oppression. “The whole world is watching.”

There is an honorable tradition of civil disobedience in America. If an injustice is so grave and the system is so rigged that it can’t be changed through normal democratic means, as in the Jim Crow South, breaking the law may be a recourse. The civil-rights protesters did it peacefully and with dignity. The difference between them and the Occupy protesters challenging the cops is the difference between self-sacrificial heroes and ideologically drunk punks and whiners.

In Oakland about a week ago, when police cleared out an encampment near City Hall, protesters fought back, and roughly 100 of them were arrested and one gravely wounded. It was all avoidable if they had peaceably complied with an order to vacate their illegal makeshift campsite. In retaliation, the protesters called for a “general strike,” a phrase redolent of revolutionary action.

The strike wasn’t anywhere close to general, since most people with jobs don’t have time for idle political indulgences. But the protesters turned out a few thousand. Even before it truly got out of control at night, protesters were smashing windows and spraying graffiti on walls. After shutting down the port, a black-clad contingent headed downtown, where they set fires and threw firecrackers, rocks and bottles at the police. In a perfect expression of wanton destructiveness, they attacked road signs.

Other Oakland protesters tried to restrain the violence, without much luck. Such is the dynamic of mobs. With no specific agenda and no standards for disentangling legitimate demands from lunacy, the Occupy movement is prone to get more extreme rather than less. A free-floating radicalism is written into its DNA.

The catchy, initial promotional poster for Occupy Wall Street designed by the left-wing magazine Adbusters depicted a ballerina standing on the iconic Wall Street bull surrounded by riot police. In its absurdist aesthetic and forecast of conflict with the authorities, the poster presciently represented the future of the Occupy movement.

Everyone acknowledges the right of the Occupiers to protest and to live however they please. They can request permits to march every day, and try to levitate the Federal Reserve building if they want. They can, in a fine American tradition, go off and create freakish communes where they hold goods in common and live in splendid squalor. But they shouldn’t be allowed to break the rules while building fetid encampments on property not their own, and their contempt for the police should be tolerated by no one.

Mere protests probably won’t satisfy the movement, though. It is a self-styled “occupation,” which inherently involves taking what is not yours. It’s already ugly and will probably get more so.