Nothing profound or original here, just a few observations:
It appears that quite large peaceful protests were largely ignored by the news media, especially outside the local area. Only when they turned violent and destructive did they excite much attention. Not only does this create a false impression about the overall reaction, it might conceivably even encourage destructive violence as a way of getting noticed.
Of course, rioting is stupid and counterproductive. The following commentary by a Baltimore resident explains that. The language in this video is definitely not safe for work, but however offensive his manner of speaking might be to many, it actually might help get across his message:
This reminds me a little of a now-common distortion of the concept of nonviolent civil disobedience. Back in the early 1960s there were protests in which African American citizens lined up to register to vote, knowing the local authorities would not permit it and would very likely arrest them (which indeed often happened). The organizers were careful to urge those taking part to make sure they did not block the sidewalk or do anything else that might justify police intervention, so that when they were arrested, it was clear that it was for exercising a basic right of citizenship. The same is basically true of Gandhi's acts of nonviolent civil disobedience, such as the boycott against British textiles and defiance of the British salt monopoly. Now it's not unusual for nonviolent demonstrators to intentionally block streets, sidewalks, public transportation, or building entrances (from college administration buildings to women's health clinics) in an attempt to draw more attention or to provoke arrest. But in such cases the arrests are not for exercising one's own rights but for denying others theirs. That strikes me as something of a different order, an assertion not of one's equal right but of one's imagined superiority, and it troubles me whether I agree with the protest in question or not. It is, of course, far better than resorting to violence, but that doesn't automatically make it OK.
Update: For something that might have helped provoke the destructiveness in Baltimore, see this later post.
Finally, we should recall that major or minor riots happen many places with even less provocation than in Baltimore, for example in response to a major victory or loss by a local sports team, as noted in this article.