The answer is:
He says that he would never help bring free and brave people into slavery.
In "Gulliver's Travels," by Jonathan Swift, the protagonist refuses to act in accordance to the Lilliputian emperor's wish to destroy the Blefuscudians. The emperor intends to become the only monarch of the world, but Gulliver claims he "would never be an instrument of bringing a free and brave people into slavery." As a consequence, he is accused of treason.