I think that Red John was once a prominent member of Visualise, hence why Brett Stiles knows him. I think he worked his way up through the ranks, but somewhere along the way corrupted the teachings of the cult. He uses his natural charm and influence along with Visualise teachings to create his own sub=group of followers. This is why he seems to have contacts all over the place including law enforcement and FBI. It's already been established that Visualise members are everywhere and don't always let their "faith" be known.

It is possible that Red John is an organisation of it's own, with the leader ordering hits on the various victims, while keeping his own hands clean at this stage. He could possibly teach his disciples his methods in order to keep the killings consistent. That would explain how his victims are killed so quickly when they are exposed as a lead (as in Red John's Friends when Jared Renfrew is already dead by the time the team reach him).

Also the message left behind "He is man" could indicate that Red John views himself as a higher power or even god-like figure, leading us back to Red John being a member of Visualise. It's possible that  Red John is bringing new members into the organisation, which is why Brett Stiles turns a blind eye to his other actions. Either that or he is Brett Stiles son, groomed from an early age to be the next leader of the organisation, and therefore been treated his whole life as a saviour.