It's been years since I watched this movie, but your post has got me thinking about Creation and Destruction...which to me are different sides of the same coin.
Creation is as much an act of destruction as it is creating something new. I've been a life long inventor and this is something I've come up against everytime I've brought a new product to market. If you create a new product, most likely it is meant to replace something that is already in use. People always say they are looking for the "new and improved", but that is rarely the case. Many people have a vested interest in the current system/product/method, like manufacturers, wholesalers, salespeople, retail and even customers...and they don't want things to change. Change is hard. Change is work. Change is scary.
Consequently, in order to bring change, one must ususally be very aggressive, even violent (depending on how you define "violence"), because you may have to destroy what is already there before the "new and improved" can take it's place.
That's what I think Ed Norton's character had to do before he could take on his new life: completely destroy his old life. His method for his change was fight club.
That, or he just went fucking crazy...I dunno.