Within any group of people, be it protest marches, or sports fans to / from games, there will Always be a rogue element out to cause trouble.
Back in the 80s some English teams were banned from Europe IIRC, This is no longer needed, we have the ability to combine intel on known troublemakers, with video footage and good old fashioned policing and hard work to ensure gatherings happen in a safe way, identify problems before hand and take action.
The Majority do not want trouble, if the police work closely with the majority they should be able to take pre emptive action.
Sadly the relationship with the police has now go to the point where there is zero trust and this can't happen.