This video (hat tip to Shanghaiist), coming after Saturday's 1-1 draw in Shanghai, is the most recent example of the urh...intensity of Shanghai soccer fans. The draw leaves Shanghai 1 point behind Shandong for the league title with only 4 games left (Beijing is in 3rd, 8 points off the title race).
The scene in the video shows some rowdy soccer fans who are having some fun, setting fire to a stuffed version of Beijing's mascot. Their chanting of the "Jing Ma", humorously, could get them in trouble if they were in Beijing. While this sort of spirit makes attending a soccer game more fun and is part of the atmosphere inside the stadium, I've seen myself what happens when it is turned on visiting fans. China's large size makes attending a soccer game similar to the US where, in most cases, there are no fans of the visiting team or just a small contingent of traveling fans and people who have relocated to that city.
There are some "derby" games, when Beijing and Tianjin play or in the old days when there were two teams in Shanghai and often there would be a certain degree of violence outside the stadium. Even now, there are times when large traveling contingents will take to trains and buses and suddenly show up in a nearby city for a match. The police is rarely prepared for these situations or turns the other cheek, though this year there was a large presence in Beijing that led Shanghai fans out of the stadium and onto their bus.
While the big incidents of Chinese soccer violence get reported only because there is no way of avoiding it (huge fights in the stands in Xian, attacking the Japanese bus after the Asian Cup in 2004, etc), there are many small examples of brawls outside of stadiums that simply go unnoticed and unreported, because there is rarely anyone around with a camera and the police doesn't want to be bothered with these "minor" incidents.
The inconsistency and lack of knowledge about how many traveling supporters will show up makes things hard for the police to prepare. I've said it before, but its going to take a death outside a stadium, something not wholly unimaginable, before police take note and step in to make fans safer. It may seem like an off the wall prediction, but when you see the unruly and excitable mass of people above, its not hard to imagine them turning violent very quickly.