Anti-fan

Anti-fans are the group of people who are opposed to particular person, system, or idea. This word is from a prefix 'anti-', which means 'opposed'. Anti-fans gather and criticize particular thing which they hate.
Anti-fans' activities are very diverse. Anti-fans usually work and share their views in online website. They make anti-fan page. E.g. anti-fan website, anti-fan blog, anti-fan internet cafe etc. And, they criticise their target, spread a rumor about the target, and post malicious comments to Internet articles. Anti-fans also work when they are offline. They sometimes boo and jeer at their target and even start a movement against the target. 
Early their activities used to be constructive criticism, but nowadays the movement of anti-fans is changing to severe insult to their target with no specific reason. The ruthless attack causes a lot of social problems now. A lot of celebrities who are the anti-fans' target are suffering from their behaviors. In some case, they may accuse anti-fans of personal insults. 
Object.
Anti-fans' targets are various. The most usual target is entertainer. There are a lot of anti-fans' website for the entertainer who they dislike. E.g. Some anti-fans oppose a form of music, movie, athlete, politician, political party, TV series, idea etc. Surprisingly, the number of anti-fans tends to be proportional to the target's popularity. Thus, the number sometimes becomes a yardstick of star's popularity.
Intelligent anti-fan.
Intelligent anti-fan is one type of anti-fans. Intelligent anti-fans act as if they are the target's real fan and do wrong and bad behaviors as the fan. They intelligently create the target's bad image and gather more anti-fan.