What was the past like, according to the grandmother and Red Sammy? How was it different from, and better than, the present?
The grandmother and Red Sammy both agree that people have changed for the worse over the years. Red Sammy is feeling moody and pessimistic because he let two "young fellers" charge some gas for their old car and they never paid him. He says, "These days you don't know who to trust." It is Red Sammy who says, "A good man is hard to find. Everything is getting terrible. I remember the day you could go off and leave your screen door unlatched. Not no more."
The grandmother agrees. She says, "People are certainly not nice like they used to be." Her own rude and unruly grandchildren seem to be living examples of the fact that people are evolving in a bad direction with the passage of time.
Red Sammy seems to believe that people used to be more trustworthy, while the grandmother seems focused on the notion that people used to be more courteous.
This little exchange foreshadows the deadly encounter that the old woman and her family will soon have with the Misfit and his fellow fugitives. The story is somewhat reminiscent of Voltaire's Candide, in which the philosopher Pangloss keeps insisting that everything is for the best in this best of all possible worlds, this in spite of the fact that everything is going wrong.