Sort out your fans england.
Ban racist or violent fans for life out of the stadium and have 0 tolerance.
Don't even sell a Ticket to someone who had previous incidents at a football match. -> Requires people to carry their identification and to track some data similar to a casino.
If hundreds or even thousands of fans do monkey sounds or storm a stadium -> Sue the club/association and/or force a ghost game with no fans in the stadium or in the fan curve.