Open fire. Shoot 5o kill.
The Army has area denial devices that will fill the bill nicely without the blowback that shooting ANTIFA will generate no matter how much they richly deserve it.
The ‘Active Denial System’ is something like a giant microwave that heats up its targets to an uncomfortable degree. Unless they are keen on seeing if it will actually cook them like a hot dog they will move along.
The Long Range Acoustic Device is another fun one, it generates sound levels that even the most ardent metal head won’t find tolerable.