Why did peter believe they had to try to help the faun?

Peter believed they had to help the faun because it was a matter of justice and compassion; he understood that standing up for the oppressed was essential in their fight against the White Witch's tyranny. Additionally, helping the faun would strengthen their alliance with the creatures of Narnia, fostering unity against a common enemy. Peter's sense of morality and bravery compelled him to act, reflecting his growth as a leader in the unfolding battle for Narnia's freedom.