Just for the heck of it, I did a search for references, in news articles, to the line "Good Fences Make Good Neighbors." Almost every article I found referencing the line attributed the line to Frost, as in "Robert Frost said 'Good fences make good neighbors.'" Then the writer proceeds to argue that because Robert Frost says it, it must be true, or that, sorry, Robert, you're wrong.
I'm starting to think that this may well be the most-taken-out-of-context line in all of poetry, surpassing even "To thine own self be true" from Hamlet. Even though Polonius's line is clearly supposed to be a stupid cliche, not to be taken seriously, at least no one explicitly points that out in the play. Whereas in Frost's "Mending Wall," not only is the line "Good fences make good neighbors" spoken (twice) by a character we're not supposed to agree with, but the narrator expressed a desire to question this vapid talking point ("Why do they make good neighbors?"). So blame Robert Frost for lots of things, but don't blame him for saying that good fences make good neighbors. He no more said that than Shakespeare advocated killing all the lawyers.
This has been a Public Service Announcement by the Enemies of Eviscerating Poetry (EEP).