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Portland Police Chief Mike Marshman appears outside Portland City Hall Friday to discuss Thursday night's violence and to dissuade protesters from continuing their marches.

(Dave Killen/Staff)

Portland's descent into civil disorder occurred sometime after 8 p.m. Thursday night as otherwise peaceful, if roadway-blocking, protesters snaked their way through town. Things got ugly in Northeast Portland, where 19 new cars at a Toyota dealership were trashed by brick-throwers, and then worse when thousands of folks walked across the Broadway Bridge and into the city's tony Pearl District.

There, the vandalism metastasized. It became athletic, wantonly opportunistic and expansive. Power sources mounted to structures were battered, sparks flying. Large plate glass windows were shattered, shards of glass raining down. Walls and store entrances were sprayed with graffiti, leaving strange signatures and symbols.

Frightened onlookers asked: Where are the police? By midday Friday, police estimated total damages at more than $1 million.

The rampage was conducted, protesters and police said, by a comparatively small number of infiltrating anarchists. It seemed plausible, given that KGW-TV's courageous live footage of the spectacle showed young men, mostly, with bandanas or other forms of face coverings, and wearing knit hats -- the better to go unrecognized. Overheard were cries from marchers to stop the violence.

But one man, if unrecognizable, was the poster boy of the night. Tall and lean, he repeatedly left-footed a large plate glass window, caving it in to applause from his cohorts before bouncing back on his feet and clapping his hands twice -- as if he'd finally found his rhythm and sunk a rimless basket from an invisible 3-point line. Except this was no game. This was real life, real property, real violence against unseen others. And it was a proud city's tattered spirit circling the drain.

Portland should have no room for hooligans, thugs and those who sully the efforts of others. The young man bent on violence, along with his expletive-shouting comrades, had no apparent connection to any of the myriad causes that brought LGBT, ethnic, global warming and other groups beneath a unifying anti-Trump banner. He was, and is, a common criminal. And he was likely getting away with his marauding deeds while becoming a star among comrades.

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A police spokesman explained to a reporter Thursday night that entering a crowd of thousands to conduct criminal enforcement against a few could backfire, creating a massive eruption fueled by fear, confusion and anger. No doubt. So events had to reach a certain threshold before police in riot gear showed up, after 9 p.m., to establish a commanding line, sending marchers on their way and ultimately arresting 26. Many of their mugshots appeared at OregonLive.com midday Friday, and it will be some time before charges, if any, can be attached to them.

But protesters already angering folks for thwarting movement about the city must take a hard and new lesson from Thursday night's carnage: The rules just changed.

Protesters, when assembled in the hundreds and thousands, must now accept full responsibility for hosting anarchists who find cover within their ranks and wreak havoc. That means stopping the event cold and retreating the minute violence erupts. That means defanging the parasites and possibly exposing them. That means clearly establishing the terms of demonstration to include the willingness to quickly disband if violence erupts.

It was heartening to learn on Friday that some protest sponsors had created a fund to pay for repair work in the Pearl. But cleanup that covers for the criminals enables and encourages. What's to stop the next batch of fools from delivering to Portland harrowing moments of civil disorder when there's no real price to pay?

-The Oregonian/OregonLive Editorial Board