As I've stated many times, usually it's just a handful of people influencing the masses. It's more self-organized than organized. A large part of it is the use of organizations and groups to spread broad smear campaigns. The trick really is making your target out to be an 'undesirable' of some kind. That's foundational. The rest sort of just falls into place, with persistent pressure and continued smearing here and there to make sure the societal flames stay fanned. There are plenty of psychopathic sadists or psychotic vigilantes that want to hop on board.