It would seem that soccer is just a fanatical game as a whole.
One of the best sports experiences I've ever had was going to a DC United game 2 summers ago. It had rained heavily just before the start of the game...and everyone was drenched. But the game was exciting, and Rho and I had a lot of fun. Some of the fans became unruly...I probably saw 2 or 3 fights almost commence. And the 2 big fan clubs, Screaming Eagles and Barra Brava, are rabid. Picture about 2000 fans jumping up and down during the entire game, screaming and yelling, making the section of seats bob up and down all night.
The funny part of that game was that there were several groups there that night, as in kids' soccer teams and their families. I know sports teams in general are trying to be more family-friendly, but young soccer fans may want to try something less violent, like indoor soccer.
World Cup starts 2 weeks from today. I remember reading on BBC about how some businesses in the UK are worried about people calling off on June 2 and 7 (England's match days), because the games start at 10:30am and 12:30pm (respectively) London time. I wonder if a) the fans will be rowdy in their respective home countries during the games, and b) if the Japanese and Koreans are as rabid as Europeans and Latin Americans when it comes to soccer.