You make a very great point, and that's exactly the heart of the matter here.
This is intended to deal with situations that, as you say, get out of hand. They become an unlawful assembly. They become a riot. It's intended to deal with individuals who are participating in and involved in those kinds of situations. It's not intended to deal with the legitimate innocent bystander, whether it's someone who is passing through the area, or someone who was part of a legitimate public gathering that's become a situation like that. It's intended to deal with the troublemakers. Police are looking to deal with the troublemakers as well. That's what their job is: protect the public from people who are looking to engage in criminal activity. Very clearly, there's no question in my mind that these are the individuals police will be focusing on.
As you said, in these kinds of situations, where the public safety is threatened, and when things get to the point where police cars are being lit on fire, storefronts are being damaged, and innocent individuals are being assaulted, police are trying to protect the public and protect property from individuals who are looking to engage in criminality. That's where their focus is going to be. They're not looking to deal with the person who's there for legitimate reasons and is looking to flee the area. They're looking to deal with people who threaten public safety.