Bill Harford is pure and good and remains so even as the events in his life conspire to make him feel powerless and small. He can't save Mandy. He can't save Nick. He can't peel back the orgy-goers' masks and understand their motives and identities, even as they learn every detail about him. He can't stop his wife from emasculating him.
Faced with an overly-sexualized and amoral world where there's no apparent reward for the righteous, a lesser man (see Ziegler or Milich) would become nihilistic and cling to power. Harford heroically accepts his lot in life and is fundamentally unchanged at the film's conclusion.
