What is the central message of To Kill a Mockingbird?

The central message of To Kill A Mockingbird is that in a way we all fragile mockingbirds - we all have our weaknesses and exposing them to the harsh realities of the world can destroy us. When Jem hears the decision of the court case of Tom, his innocence is killed, but when Boo Radley saves Jem and Scout from Mr. Ewell, they cover up the murder because Boo's reclusion is what makes him operate well. To turn in Boo would be to shatter his world completely and it is through Boo Radley that Harper Lee shows how justice is not always clean cut.