Saying obsessed or being crazy about something seems a little negative and derogatory. How am I supposed to say it in a positive way.
I would say,
"People here are complete fanatics!"
There is some debate about whether "fan," which is what sports enthusiasts are normally called, is short for "fanatic," (See NB below); however, fanatic, in full form, in the context of sports, means something much stronger. For example, you would call someone who lacks passion for their team a "fair weather fan" but not a "fair weather fanatic." Fanatic has the added punch of zealotry.
Plus, you should not confuse a Phillies fan:
with the Phillies Phanatic:
NB: There is a passage in the Dickson Baseball Dictionary which claims that "fan" comes from "the fancy," an archaic expression that referred to dapper young men in the know who were prizefighting enthusiasts. Dickson writes,
"'The fancy' was long a class in England and America for followers of boxing. Baseball borrowed it and shortened it to 'the fance,' 'fans,' and 'fan.' I do not agree with Ted Sullivan...that he originated it ['fan'] as an abbreviation of 'fanatic.'"
Whether Dickson is right that Sullivan or anyone else for that matter did not derive "fan" from "fanatic," turning up a reference to baseball enthusiasts as members of "the fancy" on the internet is difficult.
Any sports nut will not mind being called that. In fact, such people usually wear the term as a badge of honor.
For example, look at the title of this whole section on Slate Magazine.
You can call sports nuts sports enthusiasts and be neutrally negative. You don't get nastily negative until you use words like sports crazies, sports zealots, sportsophages (analogous to the Harry Potter Death Eaters), sportophagous assholes, athleticophagous, or homoludditicus neanderthalensis (my own neologism based on the term homo ludens: homo means human and ludens means playing; from Latin: "ludus — from ludere, covers the whole field of play", Luddite, and Neanderthal