Comment by bombcar

They're referring to "anti fans". You see it with online personalities especially; the most rabid fans (often parasocial, think online streaming) are the ones who will become the biggest detractors or anti fans.

Most people are "oh that's fun to watch ok" and then when they don't like it anymore, they get bored and forget about it entirely.

The anti-fans continue to follow it, but rabidly hate it.

Think Syndrome from Incredibles. He's always been the biggest fan.