Keep it simple. Can you imagine letting these clowns riot in/near the corner of Wall and Broad, and some enterprising anti-Marxist attaching a power hose to one or another sewer line vent(s) in the vicinity, and venting all those wonderful gasses right in the centre of the mob?
It would be the shortest riot in history.
(cough) Not to mention numerous other tactics that are easily and cheaply employable in such cases.