There is something I don't get. I think in general people who live in the south of US - Mexico border are nicer and friendlier than people in US. Most people I encountered are warm and have good a heart. But what do soccer fans behave like animals?
Because they're the Latin American equivalent of people who live in trailer parks or the inner-city. Europe isn't any different.
Usually what you see is exuberant passion. The passion sometimes goes too far,(when violence kicks in) and I think you'll find that over exuberance all over the world. I have an Albanian friend who tells me how violent soccer matches can get, and we all know what has happened in Italy, for example.