Why does Manley Pointer refer to Christians as Chrustians in "Good Country People"?

First, I need to let you know that I changed the spelling
of "crustians" to "chrustians" (as it is in the
text).

Manley Pointer, in "Good Country People", refers to
Christians as "Chrustians".  The reasoning behind this can be answered in a few
ways.

First, dissect the word. Crust (chrust) means a tough
or hard outer layer. "Ian" is either a suffix that refers to what someone is or does OR
is used as a suffix that forms an adjective or noun. Therefore, "chrustian" could have
two meanings based upon this: a person with a hard outer layer or a word which describes
a hard person.

Second, the story is written using southern
dialect.  The use of the word "chrustian" could simply be Flannery O'Conner using the
dialect of the area from which she bases the story:
Georgia.

Lastly, Pointer could simply be making fun of
Christians.  By the end of the story, readers find out that Pointer is not a bible
salesman, but he seems to prey on them based upon their unshakable trust of other
"Christians".