What can we make of the title of "Good People" by David Foster Wallace?

The title of David Foster Wallace's short story "Good People" (published in 2007, the year before the author's death) is lifted from the text. Let's take a look at the use of the phrase in the story. Here, Lane Dean, one of the central characters, is sitting on a picnic table next to his girlfriend, reflecting on the first time he met her:

Lane Dean had liked the smell of her right away. His mother called her down to earth and liked her, thought she was good people, you could tell—she made this evident in little ways.

We learn early in the story that Lane Dean and Sheri, his girlfriend, are unexpectedly pregnant, and they are not happy about it. They are from a relatively strict Christian community where the idea of sex before marriage is strongly frowned upon.

The story is told from Lane Dean's point of view as he sits next to his girlfriend, recounting the events that have led up to that moment and pondering what to do next. His thoughts reveal a deep crisis of conscience. He doesn't want Sheri to consider having the baby, but he doesn't want to be the sort of guy who would push her into having an abortion either. He makes many references to his faith, and to Sheri's, as in the following examples:

Sometimes when alone and thinking or struggling to turn a matter over to Jesus Christ in prayer . . .

She was serious in her faith and values in a way that Lane had liked and now, sitting here with her on the table, found himself afraid of. This was an awful thing. He was starting to believe that he might not be serious in his faith.

He kept thinking also of 1 Timothy and the hypocrite therein who disputeth over words. 

The title refers to social and religious standards for what a "good person" is and Lane Dean's struggle to know if he can continue to be good—or whether he ever was. He grapples with what is "good" and "safe" and "decent:"

One thing Lane Dean did was reassure her again that he’d go with her and be there with her. It was one of the few safe or decent things he could really say.

The meaning of the story's title is perhaps best summarized in the following passage:

He was desperate to be good people, to still be able to feel he was good. He rarely before now had thought of damnation and Hell—that part of it didn’t speak to his spirit—and in worship services he more just tuned himself out and tolerated Hell when it came up, the same way you tolerate the job you’ve got to have to save up for what it is you want.

In Lane Dean's world, good and bad are black and white; there is no middle ground. There's "good people" and there's "damnation and Hell." And he doesn't know which of the two he belongs to or how to proceed. As the reader, it's almost impossible not to feel some empathy for this internal struggle.