Not all but many. And Ivan, you well know that these 'hooligans' aren't just hot heads who get annoyed at a game and start a row. They are organised groups of thugs, who deliberately arm themselves, travel to games, and start a riot. I'd call them Britain's indigenous terrorists myself.
It is a problem, but the authorities have been getting better at dealing with it, I think. It's hard to get too worked up about it though when you have Al Qaeda threatening to release poison gas in the Tube however.
Love, Ivan