Cowardice is not a civic duty, nor a virtue. Use of force by civilians in perceived service of the law is often justified. Going out looking for a fight is one thing, serving the public is another.
Ideally, the law can be upheld without force; when force is required to uphold the law, we could ideally rely on peace officers to be ready, willing, and able to take on that burden; but in the end, it is the responsibility of society as a whole to uphold the law and prevent suffering.
When force is necessary, and when peace officers aren't around, a person who uses the necessary degree of force to rescue old people from a drone who would rather watch them wade naked in their own faeces until they go hypothermic or fall ill, than violate a workplace policy is not a vigilante, but an upstanding citizen.
It's natural to scrutinize and question the motivations of somebody who has used force, but it is a disservice to us all to hold common people to a higher standard of conduct than the police.