BEIRUT, Lebanon — In the beginning there was just an insult, sparked by a trivial squabble in a street of a working-class neighborhood of Beirut. A surly-looking man on a balcony splashes some water on a foreman below who has come to fix a defective pipe; the foreman curses back. Such is the starting point of “The Insult,” a film by Ziad Doueiri, which is up for an Academy Award in the foreign-language category on Sunday.

Matters could have ended there. After all, as Freud supposedly said, “The first human who hurled an insult instead of a stone was the founder of civilization.” But not in the Lebanon of “The Insult” — where the insult turns into a fight, then a court case and finally a state affair. And not in the real Lebanon either: Some weeks back, just a few months before the next general election is expected to be held, another insult set the country ablaze.

In late January a video appeared online showing Gebran Bassil, the foreign minister (and the president’s son-in-law), calling Nabih Berri, the speaker of the National Assembly, a “thug.” Some streets of Beirut broke out into scenes that could have been lifted from the movie: angry youth, blocked roads, burning tires — as ever, the specter of civil strife. Mr. Bassil (like his father-in-law) is a Maronite Christian; Mr. Berri is a Shiite. And the whole of Lebanese politics plays the sectarian chord.

Here, a single insult can rekindle badly healed wounds, and nudged by just a few excesses from the media or the public, push Lebanon to the brink. (Freud might have called this, too, the “return of the repressed.”) Resentment runs deep in this tiny country, this house of many mansions, home to so many communities with so many narratives forged over so many decades of frustration. Fear of a conflagration remains after a long history of deadly fratricidal clashes, for example in 1845, 1860, 1958 and, of course, 1975–90.