BJJ is a fast growing sport and its community is very tight knit and passionate. Some leading figures of the BJJ community (athletes or instructors) have a huge following which means that getting their share of ‘haters’ comes with the territory. Very often the most successful ones have an equal amount of haters as they have fans. In some other cases when the person has a bad attitude, has immoral actions , the hate of the community can vastly overwhelm the support.
Most of the hate is not malicious. Sometimes it is even fun, (Gordon Ryan case for example) whereas in some other cases there is genuine hate (BJJ personalities who have abused others).
This video illustrates the most hated grapplers in Brazilian Jiu-Jitsu history.