Fan is short for Fanatic.
That is pretty much all you need to know as you read this story from Deadspin.com.
“He just happened to think UofL would beat UK and he started to run his mouth,” explained dialysis patient Ed Wilson. Wilson also happens to be a self-proclaimed die hard UK fan. “That’s what started it.”
But Charles Taylor, who was waiting to get hooked up to a machine saw things differently. “I didn’t talk to him about the ball game; I was talking to another guy about the game,” The UofL fan exclaimed. “He was meddling. And told me to shut up and gave me the finger!”
[…]
“I wasn’t gonna take no more from him,” UofL fan Taylor said.
UK fan Wilson explained “I’m sitting there hooked up to a machine and I can’t do anything.”
So, offended by Wilson, Taylor took action. “I went up to him and I hit him, ” he said. “Didn’t hit him that hard, but I hit him.”