Well that comparison was childish. No, you do not arrest everyone in the bank, but you do arrest the getaway driver outside because even though they did not enter the bank or point a gun at anyone or grab any money, they were in on the crime, knew about it, and was part of it. The family members at home who heard them planning the robbery and did not call the cops they are also accessories of the crime and need to go to prison.
No reasonable person would stand anywhere near those throwing rocks at cops, breaking windows, looting businesses, setting cars of fire unless they liked it and wanted to be included and supportive of the crimes. Maybe you can claim them to be clueless before the first violent action, but once the violence starts if they do not run away from those people doing the violence, they are 100% just as guilty.
But I have always held this opinion, I have said for years that if you stand there and watch crime happen and do not at least call the cops and report it, you are just as guilty as those who commit the crimes. As a citizen, you have a duty to try and help keep society safe and defend each other from crimes, especially violence. If you are turning a blind eye, or you are even cheering violence on, you are just as bad as the ones doing it physically.
Let me offer you something to consider. Let’s say for the sake of argument that 10 people did all the actual violence, the rest just went along for the excitement. Do you think those same 10 people would have done all that without an army at their back and surrounding them showing them approval and support? Ever hear of the mob mentality?