See, I felt like the "the one person in the whole series to show a sense of dignity and conviction" was Rachel. Rachel fought the mob, but never condoned extra-legal vigilante justice, whereas Gordon was willing to work side-by-side with not only an outlaw vigilante but with crooked cops. Rachel was appalled by dishonesty and refused to abide by Harvey taking the blame for being Batman, whereas Gordon took part in a conspiracy to frame an innocent man for multiple homicides in order to preserve the public image of the real killer. Gordon is guilty of all the crimes Batman is guilty of, with the addition of hypocrisy, since he is a cop.
Gordon is the most morally compromised character in the whole series. Batman and Dent (before his scarring) were idealists who bent the rules in the name of capital-g Good. The mob had their own code of ethics ("honor... respect") and Ra's al Ghul was trying, in his way, to save the world from crime. Even the Joker was dedicated to his ideals of anarchy.
Gordon, however, bends and breaks the rules not out of dedication to an ideal but out of a desire for an ill-defined sense of order. Gordon represents the people of Gotham, who want security but are too scared to take a true stand against crime. The citizens of Gotham support Batman's war on the mob when it is only Batman's life on the line, but turn on Batman as soon as the Joker starts killing citizens.
This is why Gordon makes it through the movie intact and with his loved ones alive. In the Nolan-Batman-universe, idealists are doomed to smash up against other idealists until everyone is broken. The only way to avoid breaking is to bend.