A fan of a team is someone who supports the team on a regular and loyal basis ... over an extended period of time.
An anti-fan of a team is someone who ... on an equally regular and equally loyal basis ... over an equally extended period of time ... supports whichever team is playing against the team.
All teams have their actively loyal fans. Only some teams have a core of equally loyal anti-fans. Some of those teams with an active core of anti-fans include the New York Yankees in US baseball, the Dallas Cowboys in US football, Manchester United in English soccer, and the Collingwood and Hawthorn clubs in Australian football.
Now, a person who's an anti-fan of a sports team usually has nothing against the team's actual players, past or present. An anti-fan of the New York Yankees, for example, has nothing against such iconic players of the game as Babe Ruth, Lou Gehrig, Joe DiMaggio, Mickey Mantle, Yogi Berra, Reggie Jackson, Alex Rodriguez, or Derek Jeter. The thing that makes an anti-fan a true anti-fan is their reaction to the attitudes and the behaviour of some of the team's fans. Normally, the reason a true anti-fan can't stand a team is because they can't stand the arrogance and the swagger of many of the team's fans.
Now, I'll make a jump in concepts here. I think this idea of fans and anti-fans applies to religion as well. There are some people who are positively enthusiastic for a particular faith community. There are other people whose enthusiasm in the area of religious faith is mainly centred on expressing their prejudices against a particular faith community. Like the New York Yankees, Manchester United, or Hawthorn, faith communities have both their fans and their anti-fans.
And, like anti-fans of sports teams, anti-fans of faith communities (and I nearly wrote "anti-fans of faith teams") ground their antipathy toward the team not in their attitudes towards the team's "players", but in their attitudes toward the team's "fans". We rarely find this to be an antipathy against a faith's founder, against its saints and martyrs, against its scholars and thinkers, or against the many everyday people who find their faith to be a way to live with compassion and integrity.
Usually if a person is an "anti-fan" of a faith community, it's normally a reaction to the faith's more aggressive "fans", people who don't really understand the spirit of the "game", but who are, nevertheless, zealously one-eyed supporters of a faith's team:
- ostentatiously pious politicians,
- aggressively politicised clerics,
- culture warriors within the media,
- violent "redneck" types who use the faith to give a veneer of respectability to their destructive urges,
- dirty-minded puritanical types who can be found in most faith communities,
- and so on.
And, may I also suggest that, if you find yourself to be (or find yourself becoming) an "anti-fan" of any faith community, focus less on the faith's more objectionable "fans" but spend some time getting to know people within the faith who actually play the "game".