Well in my country they fight in every sport
. Soccer is just more popular, so more people to get into fight. People here don't go to watch the game, they go there to fight with someone. Apparently there is fun about this. I don't see it, but they see it.
The fightings for me are due to a lot of factors - poor economic environment (some people grew in violent environment), not good parents to learn them how to act or parents that have set the same example, missing or low education of the fans, hatred between the fans sometimes even encouraged by the players or coaches. Now in soccer the players don't fight too much (they make fouls, but they shouldn't fight) so fans need to do it themselves. I'm not defending them, but most of the people that get into fights are really not that smart, ambitious or what's so ever. This is their enjoyment as sick as it sounds and that's how much brain they have to process what's going on. They just get high adrenalin levels from the fighting I guess and it makes them happy. I have to mention also that a lot of them drink during the game and some people are easily irritated when they are consuming alcohol.
I don't want to sound bad, but Betty if your fans enjoy fighting between the players, at some point they will do the same. They will follow that example and it will get worse.
I just don't blame the soccer, I blame the people. I know that I like soccer and I know a lot of people like me who wouldn't get into fights or being violent and that counts for me. Just like everywhere else people could make it better or worse.