Hernando de Soto talks about how the Shining Path provided social services to build legitimacy in his incredible book, "The Other Path: The Invisible Revolution in the Third World": http://www.amazon.com/The-Other-Path-Invisible-Revolution/dp...
Sudhir Venkatesh also talks in his book about how drug dealers in Chicago provide similar services, in order to be not be rejected by communities inside of public housing projects. http://www.amazon.com/Gang-Leader-Day-Sociologist-Streets/dp...
Yakuza - like drug dealers and terrorists - are capable of great violence, but the photographer's point was that within the yakuza community that he experienced, violence is seen as a last resort. And that community activities that provide legitimacy is an important tool as well, in order to be accepted by the local community and also as a recruitment tool. This is definitely a common theme in the literature and my personal experience as well.
They are violent and target innocents, the Yakuza should never be mistaken for honourable.
If you tried to write the same book about MS-13 you'd be dead before you got to the second page.
http://www.amazon.com/This-Is-Mara-Salvatrucha-Americas/dp/1...