(Assuming there's some good faith there.)
Governments ought not to "control" protest crowds in a democracy. This is literally written down in the foundational-myth-papyrus of America.
By and large none of these crowds start as "violent" crowds. These are drivers, bartenders, moms, students, butterfly-collectors, tinkerers, teachers, short-order cooks -- they are citizens, calling for a redress of grievances.
The instinct and assumption that you ought "correctly to control" such people is what leads to increased tension and ultimately violence.
Source: I live in Seattle, and for nearly 10 years lived a block off of Pine St. (almost all of the pictures or videos you have seen of Seattle recently would be on the Pike/Pine corridor). I would see protest marches off my porch and on my walk to work, as well as black bloc types. I've walked home on May Day through protests a few times. The participants all start very clearly as protesters or vandals. Protesters have signs and wear their union jackets or their scrubs or their tennis shoes and khakis, or their superhero outfits, or whatever; they are there to protest. There are very, very few proper vandals to start off these things.
But you know what vandals and looters love? The chaos that ensues when forces with an instinct to "control" unleash munitions and other uses of force on the protesters. Do some protesters boil over and turn into vandals when the temperature and pressure turn up? Yes.
By the time you have a "violent crowd", you've fucked up and arguably lost the mandate of heaven.
When protests start getting gassed, everyone panics, and looters start to take advantage of the chaos. This is a natural consequence of applying tear gas to large crowds. People at the front start doing everything they can to get away, people in the back start to flee, and in the chaos, looting starts.
If you want to prevent looting, don't hose down peaceful protests. When protesters aren't panicking, they can police themselves, and stop violence before it happens. There's no shortage of videos and anecdotes of protests actively stopping looters/instigators, because they don't want their protests to turn violent.
The first rule of policing is that the police are the public, and that the public is the police. The only difference is that one gets paid to do it full-time.
All this flies out the window when the grenades start flying.