What does maycomb folks are the safest folks in the world mean in chapter 22?

In Chapter 22 of "To Kill a Mockingbird," the statement "Maycomb folks are the safest folks in the world" is said sarcastically by Atticus in response to Mrs. Merriweather's contradictory belief that the people of Maycomb are the most backward group in the world. Atticus is highlighting the hypocrisy and ignorance of some Maycomb residents who judge others while turning a blind eye to their own faults.