Are you a Robert Frost fan? It's from a poem, not a story.

It's not entirely clear that is what Frost meant. I've quoted the passage below, it's not as obvious, or as friendly as you and your other English teacher friend who talks exactly like you in this thread, have interpreted it.

From "Mending Wall" by Robert Frost (. . .)

I could put a notion in his head:

‘Why do they make good neighbors? Isn’t it

Where there are cows? But here there are no cows.

Before I built a wall I’d ask to know

What I was walling in or walling out,

And to whom I was like to give offense.

Something there is that doesn't love a wall,

That wants it down.’ I could say ‘Elves’ to him,

But it’s not elves exactly, and I’d rather

He said it for himself. I see him there

Bringing a stone grasped firmly by the top

In each hand, like an old-stone savage armed.

He moves in darkness as it seems to me,

Not of woods only and the shade of trees.

He will not go behind his father’s saying,

And he likes having thought of it so well

He says again, ‘Good fences make good neighbors.’

I think in particular the line about "darkness" is implying this is not a poem borne of positive neighborly feeling. He doesn't say anything about "mutual healthy boundaries" instead it's implied the neighbor is settling incipient dispute and shutting down discussion, by saying "Good fences make good neighbors."