It's all fun and games until someone gets thrown out of the stadium.
When it comes to professional sports, there are fans and there are fanatics. A sports fan boos a ref when he makes a blown call. A sports fanatic flies into a berserker rage and threatens the ref's family.
The word "fan" is derived from the word "fanatic," but there is a huge difference between the two. According to the dictionary, a fanatic is a person whose enthusiasm or zeal for something is extreme or beyond normal limits. A "fan" is a person who just really likes something. When it comes to football or baseball or basketball, a "fan" roots for the home team and a "fanatic" chants like the high priest of an ancient death cult.
Generally speaking, sports fanatics ruin sports for fans and their families. These obnoxious freaks make the games about themselves and their fragile egos. Relax, sports fanatics! Don't take a contest between groups of beefy men chasing balls around a nice park so seriously. That's just dumb.