Sport seems to have become more and more popular in society and it has led to violence between rival fans. This would never happen in music or theatre, for example, fans of Les Miserables don't attack fans of Phantom of the Opera! Because of the emphasis on sports culture, fans get riled up and are encouraged by the press to become defensive about their own team.
Yes, society puts too much importance on sports. The rowdy fans arrested in Arizona are just the latest manifestation of fans taking sports too seriously. People should stop taking games so seriously and should just sit back and enjoy them. Sports are meant to entertain fans, not to make them rowdy and destructive.
I do not believe the importance of sports has been fostered by society, at least not the individual in society. If you look at our major league franchises, especially in football and baseball, you can see that these sports are highly promoted. People pay high prices to see these games and the leagues put out tons of merchandise each year, along with tons of advertising. The companies and people who profit off of sports have put too much importance on sports, the masses simply follow.
I believe the rowdy fans in Arizona and anytime fans get out of control before and after a game, is usually caused by a good amount of alcohol and poor judgement. Especially in Arizona, these are mostly drunk 18-22 years olds who tend to get rowdy about the most innocuous things. Society does have a large importance on sports but not enough, without other factors, to induce rioting.