Shame plays a significant role in Plato's Gorgias. After Gorgias is backed into a corner by Socrates, Polus diagnoses Gorgias's mistake as one of shame (461b): Gorgias was ashamed to say what he actually thought, so he conceded things to Socrates that led to inconsistency. This leads to discussing whether oratory is admirable or shameful, with Socrates arguing that oratory is a kind of flattery, and therefore shameful. This in turn leads to discussing whether getting what you like is admirable or shameful, and Socrates' extremely important claim that doing bad is always worse than enduring it. Polus denies this, but as Socrates is able to get Polus to concede that doing wrong is at least more shameful, he is able to back Polus into a corner as well.
Callicles then diagnoses Polus's problem (482c-e): Polus also was too ashamed to say what he thought. More precisely, he claims there is a difference between natural justice and conventional justice, and Socrates is oscillating back and forth between the two in order to create awkward situations in which someone would have to say something that sounds shameful. And in natural justice, it is more shameful to endure evil than to do it; Polus, however, was stymied because in conventional justice the reverse is true. Socrates is really the one who should be ashamed, because practicing philosophy as a man is shameful (485b). The proof of Socrates's shameful state, in fact, is that somebody could bring him to trial and get him put to death, and he wouldn't be able to do anything about it.
The way Callicles had argued had suggested that he was putting himself forward as someone who could not be made ashamed of what he said. Socrates is able to prove that this is not true (494e); Callicles again tries to use shame as a weapon for herding Socrates, but Socrates isn't turned aside; Callicles cannot, in fact, maintain his distinction between natural justice and conventional justice. More importantly, he argues that while Callicles is right that his philosophy will lead to his death, this is not a matter of which to be ashamed. Only one thing is shameful: doing what's unjust (522e).
Thus there's a fundamental difference between how Socrates and how the orators see shame. For the orators, shame is a way to manipulate people, to herd them into a corner. This is why Callicles assumes that Socrates is trying to do this. But the orators come up against a wall in Socrates, because Socrates cannot be herded by shame. Believing that nothing is shameful except wrongdoing -- real wrongdoing, not even apparent wrongdoing -- Socrates cannot be manipulated. And it is also the secret to Socrates' consistency: only injustice is shameful, and therefore Socrates, who never stops considering justice and injustice, is really the man who can say what he really thinks.
