The idea that protesters should be collectively responsible for the small number of people who engage in violence or property damage lacks merit. On the other hand, the same logic does factually work when it comes to police officers engaging in brutality, racism, and other misconduct.
Starting with some legal history, Respondeat Superior is a longstanding legal doctrine whose Latin words roughly translate as “let the master answer.” It is a doctrine that uses vicarious liability to make an employer responsible for the actions of a subordinate who is acting at the direction of the employer. In essences, the idea is that a person who is harmed by an employee doing the biding of the employer should be able to hold the employer responsible for that harm.
The crux of Respondeat Superior is that the employer is benefiting from the employee doing their bidding, that the employer has the ability to control the employee through their power to hire/fire/discipline, and that the employee’s bad act was something within the general duties of their employment.
Applying this sort of reasoning to protesters and rioters
It is plainly apparent that the Respondeat Superior reasoning doesn’t fit the scenario when a rioter engages in violence or property damage and then some people try to blame protesters as a whole (or the organizers of the protest who have not committed any crimes). Protests are events that take place in public where anyone can walk up and protest (or commit a crime). The protest organizers and attendees do not employ rioters and cannot control the conduct of random people who show up in a public place at the same time as the protest. Nor are rioters doing the biding of the protest organizers who desperately want peaceful demonstrations. Indeed, the private actions of a looter who is stealing shoes for themselves does not advance the interests of the protest organizer one bit. Protest organizers and attendees cannot fire the rioters the way that an employer can fire an employee, and again cannot exclude them from the public space in which the protest is taking place.
Every aspect of the Respondeat Superior test fails, and so imposing vicarious liability (legally or morally) upon peaceful protesters and protest organizers for the actions of rioters makes no sense. Instead, it is just a means of trying to ignore the much-needed police reform and injustice that led to the protests by smearing the protesters.
Applying this sort of reasoning to police
A place where Respondeat Superior does fit is the police. Police officers are employees of the police department. The police chief and others within the government have the authority to hire, fire, and discipline police officers. Police use department-issued badges, uniforms, guns, cars, handcuffs, etc. When a police officer uses force they are doing so in the scope of their employment, using training that they were given at work. When they exceed the scope of what is proper by engaging in brutality or racism, they are still acting within the time and space of the agency relationship between themselves and the department. Respondeat Superior fits like a glove.
That is all the more true when police chiefs and other governmental actors choose not to fire bad cops who have engaged in misconduct, only to have them commit further abuses. Similarly, police officers who have sworn an oath to uphold the law yet choose to ignore misconduct on the part of other police officers, and themselves culpable.
For all the reasons expressed above, it makes no sense to blame protest organizers and attendees for the criminal actions of a few rioters. However, it does make sense to hold police departments, police chiefs, and other police officers accountable for the actions of police officers who commit misconduct.
Finally, please note that a lot of the so-called “protesters” committing acts of violence and property destruction are either made-up stories or acts of violence/destruction that were later found to be committed by white supremacists who are trying to smear the protesters. More information on that issue can be seen here: https://www.learnaboutguns.com/2020/06/22/white-supremacists-falsely-accuse-black-lives-matters-protesters-of-violence/