In Lucas' rough draft script there is a constant theme of the intertwining of the heroic and the monstrous. Figures from earlier films who were once deemed monsters now become Lucas's heroes.
R2-D2 is a Wellsian Martian tripod; C-3PO is the robot from Metropolis; Han Solo is the Creature from the Black Lagoon; Chewbacca is King Kong.
Prince Valorum is a Black Knight and a traitor to his Imperial masters. Annikin Starkiller is a wild and fierce warrior in the vein of Conan the Barbarian, an unstoppable force of bloodshed when roused to anger. And even Princess Leia is represented as the Whore of Babylon.
What gives?
Likely Lucas had in mind the original Japanese title of The Hidden Fortress. As famed Kurosawa scholar Donald Richie points out in a book Lucas owned, the title in Japan is actually Three Bad Men in a Hidden Fortress.
The "three bad men" are the two peasants, Tahei and Matashichi, and the Princess's protector, General Rokurota Makabe (played by Toshiro Mifune). The peasants are obviously "bad," for they are both cowards who complain when put to work, and they argue with each other constantly. They would gladly ravish the Princess and steal her gold in a heartbeat--if only they could agree how to divvy the gold up.
But General Makabe is bad too. He is bad, Richie argues, because he is so consumed by his devotion to his duty--serving the Princess--that he has lost all human feeling. He turns his own teenage sister in to the authorities hunting for the fugitive Princess Yuki, lettting her be executed as a decoy to throw the enemy off the trail of the real Princess.
This is arguably also the failing of General Skywalker, the Rokurota Makabe character, in Lucas' rough draft. Skywalker doesn't even blink when Leia's mother and her entourage commit suicide via nuclear blast.
Apparently Lucas felt that, in keeping with the spirit of Kurosawa's film, each of the other heroes he added to the plot should be "bad" in his or her own way too. In some cases this extends only to outer appearances, but in others (Annikin Starkiller, for instance) the descriptor is quite apt.