The phrase appears in Freud’s Civilization and its Discontents. In explaining this to students, I used to use the example of Trotskyist sects that reserved a special hatred for other Trotskyist groups. But now I have found a better example, from Mary-Ann Kirkby’s memoir I Am Hutterite:
The cultural and religious differences between the three groups were minor, confined more to dress code than religious principles. To an outsider the discrepancies would hardly be discernible, but to the Hutterites they were so significant that intermarriage between the groups was rare. The Dariusleut in Saskatchewan were committed to simple buttons on their shirts and jackets, but the Schmiedeleut in Manitoba, which included New Rosedale, considered buttons too flashy, and opted for invisible hooks, eyes, and snaps. The Lehrerleut were the most conservative, insisting the zipper of a man’s pants be at the side rather than the front, in case some unmindful man forgot to zip up.
peakmemory 
There’s a wonderful quote by Edward Gibbon in “Decline and Fall of the Roman Empire” to the effect how a single vowel affected the course of Christianity. I wish I could find that quote (read it years ago)
I think I found a reference to it here:
https://books.google.com/books?id=zexBAwAAQBAJ&pg=PA165&dq=vowel++Christianity+gibbon&hl=en&sa=X&ved=0ahUKEwihyvWrzYLPAhWEKh4KHd7MAoIQ6AEILTAD#v=onepage&q=vowel%20%20Christianity%20gibbon&f=false
Thanks for the tip!
Yes, that is what I was referring to. Gibbon spoke of “the furious contests which the difference of a single diphthong excited …”