Quote 1
"Two fellers come in here last week," Red Sammy said, "driving a Chrysler. It was a old beat-up car but it was a good one and these boys looked all right to me. Said they worked at the mill and you know I let them fellers charge the gas they bought? Now why did I do that?"
"Because you're a good man!" the grandmother said at once. (36-37)
The grandmother, barely knowing Red Sammy at all, is awfully quick to call him a "good man." Why does she do that? Does the grandmother really mean it, or is she just trying to charm Red Sammy quickly? Does she play fast and loose with the word "good," and apply it to everyone she deems "respectable"? Does she think Red Sammy's good because he was trusting and willing to help decent-seeming people? However you look at it, the grandmother appears to use the word flippantly.
Quote 2
"A good man is hard to find," Red Sammy said. "Everything is getting terrible. I remember that day you could go off and leave your screen door unlatched. Not no more." (43)
When Sammy complains that a good man is hard to find, he seems to mean that trustworthy people are hard to find. To him, "good" means "decent" or "respectable," like it does for the grandmother. Of course, the grandmother – herself certainly a "good" person – and the family will encounter somebody who's "the other kind," (see "What's Up with the Title?"), so there's something humorous yet foreboding about what Sammy says. But there's also a more serious irony because the encounter with genuine evil will pose the question of what it really means to be good. It could be that it means a lot more than Sammy or the grandmother think it does.
Quote 3
"These days you don't now who to trust," [Red Sammy] said. "Ain't that the truth?"
People are certainly not nice like they used to be," said the grandmother. (34-35)
Both the grandmother and Red Sammy seem to think that people of "this day and age" are worse than they used to be – less decent, less respectable, less trustworthy. For both (and for Red Sammy's wife), good people are hard to find nowadays because there's been a decay in the southern culture and in manners.