Violence and Sports

I don´t like watch sports at television, I prefer play it with my friends. That´s why I can´t understand why some people become crazy when a match starts or why they are monothematic about sports or how can some guys pay millions of dolars for a football player while fourth three parts of the population live with no more than 10€ per week.
Some people say that violence is connected with sports but i don´t think so. From my point of view, football is really connected with violence but there are no fights between tennis players fans. Why does it happen?
My answer is that television manipulates our acts. if television didn´t exist, there wouldn´t be so many fights because of football.
But I think that I´m criticicing football a lot... There are other countries which have problems with violence in other sports like boxing, hockey or muay thai. That sports make me think that, sometimes, violence becomes an habit and that´s very dangerous because it is more difficult to eliminate.