Expecting Facebook to have a role in policing this is just silly, it's armchair politics at its finest. Even if Facebook didn't exist, these people would have gotten together to defend their city. The solution here isn't to stop people from defending their city, it's to stop people from crossing state lines to terrorize communities for the actions of police officers, especially when there's a grey area as to the illegality of the policing action.
Media companies that pretend otherwise are throwing fuel on the fire by covering for the mob. Do they hope they'll be spared? The number of burnt businesses with BLM signs on the front in Kenosha should be a pretty good indication that you can't prostrate yourself before the mob and assume that it will result in your property being spared.