Oh my god, I know - it absolutely shattered me in the film, and the graphic novel version does the same. Have you read any of the rest of Alan Moore's work? The man has some sort of hotline into both how the world is and what our hearts desperately want the world to be, and a way of articulating it that - not to sound pat - is honest-to-Christ mindblowing. Not so much world-altering as bringing a sudden and gut-punching clarity/understanding to your own beliefs, your own dreams for all of us.

(Forgive the incoherence; it's 10am, and I'm not just-awake, I'm still awake.)

Anyway! If you haven't read his work, V for Vendetta is the obvious suggestion, but I really-truly (and really-literally) cannot recommend Promethea and Watchmen highly enough.