A proper police response to an “unruly assembly” like this can now be to arrest the entire mob.
Technology now provides a means to do so. There are now commercially available surfactants that can be sprayed on both asphalt and concrete, that make them too slick to walk across. This means that in an urban situation, where the only exits are on streets or through buildings, it could take far fewer police to arrest the entire mob.
Once deployed, with cops on the streets and covering the exits of buildings, the mob literally has to leave on their hands and knees. They cannot overwhelm the police with sheer numbers.
And this is not a theoretical technique, either. After the Rodney King riots, the LAPD obtained a number of 55 gallon drums of this kind of surfactant for just that purpose.
Wear snow grips on your shoes.