What evidence of Twain's cynicism is in Huckleberry Finn?

A major one is the constant brooding of Huck about how bad he is for "stealing" Jim away from his owners. It is obvious to everyone that Jim is a good man, a caring father, a human being who should never be owned as property. But Huck is torn apart by his moral dilemma. He has aided in robbing someone of their possession. Twain is obviously hammering it home that it is our moral duty to free these people, but reminding us that people had a completely different way of seeing the situation.