It should be noted that, for millennia, violence and destruction are considered perfectly acceptable means for accomplishing political objectives. But only when performed by state actors, of course.

IMO: the riots start out as protests. Then a minority of people choose to cause mayhem. Another minority are criminals and they do what criminals do, which is act opportunistically. And yes, agents provocateur do exist.

But sure, I can understand why people who are directly affected would prefer to have no protests at all out of fear that a riot might happen. They love order more than justice, an attitude which, ironically, has helped to create the very same conditions that people are protesting.