Over the weekend, a San Francisco police officer sent me a video of some scenes from the Black Friday protest in San Francisco. It isn’t a police video, just images shot by a bystander and posted on YouTube.

It isn’t easy to watch. (You can see it on SFGate.com. Warning, the language is uncensored.)

The edited video begins with four officers on the sidewalk, handcuffing a suspect. A crowd has gathered and is catcalling the officers, yelling, “Let him go!” Later in the video, we learn how this started.

While the cops’ backs are turned, someone off camera throws a traffic barrier at them. It’s the kind that looks like a sandwich board, but it is clearly heavy. It catches one of the kneeling cops on his helmet and shoulder and knocks him over.

One of the four cops leaps up and rushes toward the protester. But in the rush, the officer’s feet get tangled. The crowd whoops and laughs as the officer stumbles down in a heap. From there we see scenes of windows being broken, obscene chants and later, a second cop hit by a traffic barrier.

All in the name of outrage and justice, right? Police Chief Greg Suhr doesn’t buy it.

“There were 10 times more people after we won the World Series” a month ago, he said. “People say there is outrage. Well, they did the same thing after we won a baseball championship. How does breaking into an electronics store and stealing laptops help Ferguson?”

In the video, the scene shifts to a guy in a ball cap who walks up to a line of officers standing in front of a jewelry store on Powell Street, half a block from Union Square.

“Cowards!” he yells. “Cowards!” He spits at them.

When an officer breaks away to stop someone from vandalizing a store, the crowd swarms around him, taunting and jeering.

About halfway through the 5-minute video, we see how the first scene started. A white guy holding his phone steps up to a cop, presumably to record video of the moment. He puts his face inches from the cop and barks, “F-you,” 10 times.

The cop shows no reaction and walks around him. But then something happens that you can’t really see. A push? A punch? The final straw? The cop spins around, grabs the guy by the throat and says, “You are under arrest.” Three other cops put the guy down, subdue him and, with the crowd shouting, handcuff him.

That’s when the traffic barrier hits the officer in the back. And minutes later, when they have gotten the suspect to his feet and are taking him away, the barrier flies in again, hitting another cop in the head and shoulder.

You don’t have to go far into the 5-minute, 53-second video to decide that these are people who came to break things. Suhr says police made 79 arrests, six of them juveniles, out of a crowd of troublemakers that he estimates “were probably twice that.” And, he says, 50 of those arrested weren’t San Francisco residents and six weren’t even from California.

“I couldn’t be more proud of how professional and restrained my officers were,” Suhr said. “But I don’t expect one of them to endure a physical assault. When you see criminal acts, the First Amendment demonstration is over. It’s a foregone conclusion we are going to take action. It’s a question of when.”

Now, let’s be clear. The shooting of unarmed Michael Brown in Ferguson, Mo., and the subsequent grand jury process was a disaster and an embarrassment. I don’t know anyone who doesn’t feel that way, probably including some of the SFPD.

“It is not lost on the officers that there are people profoundly outraged,” Suhr said. “There are police officers who do not fully understand what went down in Ferguson.”

And I’m willing to concede that people of color, who may have been stopped and questioned by the police for no reason, probably have a very different view of the police than someone like me.

But if you’re going to make the case that San Francisco officers were too heavy-handed, or that they should have stood aside and let the looting and window shattering play out, you have lost your sympathetic audience.

Take a look at that video and tell me that attacking cops who had nothing to do with the Ferguson shooting, 2,000 miles away, was a reasonable and justifiable response. If so, I’ve got a tip for you. You are in the wrong city.

This isn’t Oakland.