To me Fight Club was not about violence, nor about enlightenment, but about an idealised version of your self. It was about the conflict and distinction between the Lesser Self and the Ideal/Greater Self. What you had was a guy who believed he could be better than himself.
The Lesser Self and the Greater Self were the same person acting out the weaknesses and strengths of the main character. The Lesser Self is who the main character is at his worst. The Greater Self is who he wants to be, the strong, charismatic, energetic, motivated and influential guy with a can-do attitude. This is in contrast with the Lesser Self who is pessimistic, lacking in self-esteem, tired and exhausted.
The Lesser Self is just a spectator watching things happen. The Greater Self mobilises armies of saboteurs, obedient minions who do what he says because he's the leader, he's the source of meaning and direction, the one who works for the greater good and leads them to it. The Lesser Self is horrified at what the Greater Self does. The Greater Self is so powerful, destructive, perhaps even vindictive, reckless, cocky and arrogant.
The recklessness of the Greater Self can be seen in the Casanova-like passion he demonstrates when he's having sex with his girlfriend. The sex is so violent that it shakes the walls of the house. Yet all the passion he shows is futile and his girlfriend doesn't get her satisfaction. They seem to have a communication problem. There's no intimacy. It's just sex.
The Greater Self tells the Lesser Self that he is never to tell his girlfriend about the Fight Club. This is the main character hiding a secret. He divides himself into two personalities, the Strong and the Weak. The main character pretends that the Strong Man and the Weak Man in him are an organisation. The god-like Strong Man (the boss, king, emperor, CEO) tells the minion-like Weak Man (employee, subject, servant) to not reveal the secret. The main character is trying to convince himself that he's smart and not a jerk, telling himself he isn't an idiot. The main character is telling himself how great he is.
The outside world sees the Weak/Lesser Self, but the main character sees the Strong/Greater Self. The Fight Club is a secret organisation that the main character uses as a demonstration of his power. He wants his girlfriend to know about it -- eventually -- after he causes the credit card companies to collapse.
The Greater Self is indeed quite powerful. He warns the authorities to beware of the main character -- the absurd notion of the same person telling the authorities to beware of himself. Even when he starts punching and fighting himself, they still don't start thinking he's insane.
Having said that, Fight Club could be thought of as a journey down the road to insanity. If such a person really existed in real life, they'd be delusional.
But . . . just like the antagonist says in one of the James Bond movies, the distance between insanity and genius is measured only by success.
