Do you remember when an occasional drunken fan would jump out of the stands at sporting events and run around the playing field until subdued by security guards?

You never see that any more. Why? Because every television organization has a standing order that when fans jump on the field, the cameras turn away.

It does not take a media scholar to conclude that the reason the offenders disrupt the game is mainly to get their antics broadcast on television.

Drawing on this lesson, we need a moratorium on live coverage of street demonstrations, especially in Oakland and Los Angeles.

Since the verdict was delivered in the George Zimmerman trial in Florida, roving bands of hooligans have taken advantage of protest demonstrations to go on the rampage in downtown Oakland and in sections of Los Angeles.

They have broken windows, damaged other property, attacked journalists and seriously injured a waiter in an Oakland restaurant who was battered with a hammer.

They have played havoc with traffic by blocking streets and attempting to force their way onto freeway on-ramps. Honest citizens are afraid to go to work, shop or go about their normal lives, because they think the streets are unsafe.

This violence is being provoked by the presence of media, live TV cameras in particular.

Would such a moratorium be unprecedented? Not at all. Avoiding inflammatory coverage allowed some cities in the South to desegregate their schools peacefully without provoking riots during the civil rights struggles of the 1960s.

This was managing the news, but it worked.

Early in my career I worked at the Louisville Courier-Journal, where Mark F. Ethridge, editor of the Courier-Journal and the Louisville Times, had sat down with the superintendent of schools on the eve of desegregation. The two decided they would not let Louisville replicate the mistakes of Little Rock in 1957, when mobs prevented black students from attending high school.

In Louisville, news organizations reported the bare facts if arrests were made, but no lingering images of hateful mobs hurling racial epithets. The schools were integrated peacefully, and a community was spared the scars that might have taken generations to heal.

Given Oakland's weakened police force, the city has emerged as a soft target for roving bands of toughs, who say they are protesters, but they are simply rabble without a cause. According to accounts from residents and business owners, these vandals are mostly white and do not live in Oakland.

They would not be out there except that they want their wanton acts to play out on the big media stage.

Their enablers are television and to some degree newspapers and other news organizations, who instinctively answer the call of the bell like the fire engine horses of old.

It's time to rethink this whole ruinous cycle.

One would have expected that by now, the ladies and gentlemen who made the decisions on news coverage would have figured out that they are open to manipulation by a mob.

Think back to the Occupy Oakland demonstrations that paralyzed Oakland for weeks in October of 2011. A protest movement eroded over time into a lawless free-for-all. As the dark carnival unfolded in Frank Ogawa Plaza and became more violent and threatening, the original nonviolent proponents quit the field, leaving behind the hard-core street people who held on until they were evicted by police.

Nevertheless, Oakland's weakness and ambivalence in dealing with the Occupy Oakland hooligans was exposed, and the Zimmerman verdict supplied the pretext for a renewed assault on a vulnerable target. Unless steps are taken, this dangerous trend will continue and spiral into worse disruptions.

Live coverage of events removes editorial judgment from news professionals and hands control to the most extreme actors in the drama. "The Camera Never Blinks," as veteran anchor Dan Rather noted in choosing the title of his book.

There is no delete button when you are going live.

William Drummond, professor of journalism at UC Berkeley, is a former reporter at the Louisville Courier-Journal and the Los Angeles Times.