n. A person who passionately dislikes a celebrity or other well-known person or entity.
Other Forms
Anonymous death threats against Kathy Sierra, a popular Web developer, author and blogger who encourages people to consider human behavior when designing technology products, have ignited the blogosphere. …

[Tara] Hunt sees Sierra as a victim of what she called the "tall poppy syndrome," meaning that "the people that stand out tend to get anti-fans. For women in particular, the threat of sexual violence is more often carried through against them."
—Dan Fost, “H Chronicles,” The San Francisco Chronicle, March 28, 2007
In the tradition of Martha Stewart before her, conquering the domestic universe can lead to fame and fortune. It also leads to caricatures, parodies and anti-fans. It seems Rachael Ray has become the kitchen maven thousands love to hate.

The anti-fan Web site gets between 150,000 and 300,000 hits a month, with anti-fans making fun of everything from Miss Ray's expressions ("Sammies" for sandwiches, for instance) to her enthusiasm when she tastes food (the ubiquitous "Yum-o") to her kitchen mistakes to her wardrobe choices.
—Karen Goldberg Goff, “Kitchen kitsch,” The Washington Times, February 18, 2007
1983 (earliest)
The Yankees' success has always made for a hard core of anti-fans.
—William B. Mead, “The official New York Yankees hater's handbook,” People, May 23, 1983