I am not sure if you're referring to this, but I have seen so many instances where an individual joins a community and then systematically tears it apart by calmly and coolly promoting ideas that ~51% kind of like and ~49% absolutely hate, through a combination of personality cult and back-room coalition building. I have seen this happen in forums, IRC channels, RPG groups, businesses. It is a particularly insidious type of toxic personality because you can't fix the problem by excising them without alienating and losing a large chunk of your community.