There doesn't seem to be a very high-barrier-to-entry for "antifa" "membership" (or name-calling).
And if you're really mostly concerned about physical attacks from "the culturally incompatible" hoards, data indicates that the "outsiders" are much more likely to be victims of violent crime than they are to be perpetrators of violent crime.
Hummm...couldn't be because they are afraid to call the police on their perpetrators since they themselves could face potential consequences.
In many cases, distrust of the "local authorities" is warranted.