Answer: when a writer points to a problem caused by social customs without explicitly challenging those customs.
A social commentary is the use of rhetorical devices in order to comment on the problems of society. This is usually a critique, and it is intended to promote change or to appeal to people's sense of justice. However, when this commentary is done subconsciously, the writer points towards the problem but does not explicitly challenge the customs.
The main idea of the book/movie twilight is YoUlL FiNd TrUe L0vE
If you're trying to write a story that "ends with the words: How wrong he was" you may want to make the story about some kind of stance you make that he disagrees with. You could choose any topic that usually creates tension between people, such as politics or the environment.
Ethos - credibility/ethics
Pathos- emotions
Logos- logic/facts/reasoning