I will make another point breifly mentioned by sshawnn. As someone who has played and coached a lot of football (American for those of you outside of the U.S.) I really enjoy watching the strategy and creativeness some coaches and players demonstrate. This includes watching some games where I have no emotional connection to either team, but just an interest in some strategy or player.
While there are negatives that go along with being a sports fan, I think the ones you list are rather minimal and rare. I don't think 1-4 are that big of a deal.
1) I highly doubt these people would exercise if there were no sports on.
2) While true, it seems a little far fetched to say it desensitizes people from war. If it does it would have to be dead last on the list of things that desensitizes or prevents people from understanding the effects of war.
3) I don't see anything wrong with wasting some time. Not everything has to be productive.
4) If the rest of the week is quality food then a bad meal or two during one or two sporting events isn't exactly horrible.
5) Definitely an issue for some poeple, but not the majority.
I do think some people take it too seriously. Philadelphia being a prime example when they actually put a jail and judge on the premises during Eagles football games, because there were too many fights and other issues during the game. I don't think they still do that. It's interesting that Philly is both a positive (jenny's) and negative example. Very passionate town.
I have also seen very high quality fan interaction between different team fans. Go to a Nebraska college football game some time and you will see some very classy fans. They always cheer for the opposing team when they run onto the field and have been known to cheer for the opposing team on a good play that goes against Nebraska. If this could be taught to the rest of the sports world, watching sports would not be a waste of time.