What reasons does Mr symmes giver for not returning Eliza and Harry to their masters?

Mr. Symmes argues against returning Eliza and Harry to their masters based on moral and ethical grounds. He believes that the institution of slavery is fundamentally wrong and that Eliza's and Harry's desire for freedom is valid. Additionally, he expresses concern for their well-being, suggesting that they would suffer if returned to a life of enslavement. Ultimately, he prioritizes their rights and humanity over the legal claims of their masters.