He's talking morals after abandoning his wife in a roadside diner.
He tells the anecdote of his mother because he thinks the boy is wrong for fleeing his mother. It's not ironic since Mr. Shiflet does it on purpose. Ironically, he is blaming himself for abandoning his mother, who was a divine gift. He recently left his wife at a diner. He should know better than to abandon people...
My friends decorum is quite fine,
he is voracious and never supine
a quandary's posed
with the picking of nose
but the rest of the time he's divine
Answer: I also live in Pennsylvania and here's what our state looked like exactly 100 years ago.
Hope this helps <333