What quotes in Huck Finn are difficult to understand by the reader and are challenging for an argument?

There are many small episodes in this picaresque novel that are easily missed by the casual reader and provide a topic for a lively debate.
One such episode occurs in chapter 16, when Huck is able to keep two slave hunters at bay by pretending that Jim, who is in the tent on the raft, is his father and afflicted with smallpox. The men see that Huck is a young boy in dire need of help, but their own self-preserving instincts prevent them from actually getting close enough to help. Instead, they float over two $20 gold pieces on a board and tell Huck,

Now we're trying to do you a kindness; you just put twenty miles between us, that's a good boy.

This episode invites a debate about people's approach to charity. Is Twain suggesting that people are willing to throw money at a problem or hardship but not get personally involved? Is he suggesting that people must take care of themselves first and only help others in small and temporary ways?