That line could have several implications.  First, it could imply that the townspeople had to find someone who did not know Miss Emily to attempt this task.  Those within Miss Emily's church might have refused knowing her character a little better.  Or, the line could be a snub towards Miss Emily's Episcopal upbringing (implying she was obviously not raised right as evidenced by her behaviour).  One element of this work is Faulkner's portrayal of the South, and the divisions in religious denominations would have been culturally apart of that.