Rather unsurprisingly, when protests occur, police frequently provoke violence:

The violence that turns a small-town protest into a fiery national spectacle like the one that has played out this month in Missouri is often unwittingly provoked by police, according to researchers at UC Berkeley.

The research team, which studied clashes between police and activists during the Occupy movement three years ago, found that protests tend to turn violent when officers use aggressive tactics, such as approaching demonstrators in riot gear or lining up in military-like formations.

Recent events in Ferguson, Mo., are a good example, the study’s lead researcher said. For nearly two weeks, activists angered by a white police officer’s fatal shooting of an unarmed black teenager have ratcheted up their protests when confronted by heavily armed police forces.

“Everything starts to turn bad when you see a police officer come out of an SUV and he’s carrying an AR-15,” said Nick Adams, a sociologist and fellow at UC Berkeley’s Institute for Data Science who leads the Deciding Force Project. “It just upsets the crowd.”

Adams said many law enforcement agencies aren’t aware that they set the tone of a protest and end up inflaming it.

I disagree with the last point.

I think that police are very aware that militarized responses encourage protests to turn violent, and that this violence gives a justification to engage in kinetic action to break up the protests.

This has been the norm for police-protest interactions ever since the mid 1800s, when police were used to crush organized labor.