This scene is nicknamed "The slap heard round the world" - From "In the Heat of the Night" (1967) with Sidney Poitier as a Philly detective investigating a murder in the deep South, which played in theaters at the height of racial tensions & civil rights protests
Here's a more detailed take:
"The film contains a famous scene in which Tibbs and Gillespie visit the home of Eric Endicott to question him, following Tibbs' discovery of trace evidence in the murder victim's car (a piece of osmunda). Upon discovering that Tibbs is suggesting he murdered Colbert, Endicott slaps Tibbs. Tibbs slaps him back. Reportedly, Tibbs's action was originally omitted from the screenplay, which stayed true to the novel with Tibbs not reacting to the slap. However, when Poitier read the script, he was purportedly uncomfortable with that reaction, as it was not true to the values his parents instilled in him. He requested that the producers alter the scene to Tibbs slapping Endicott back. This was important because of the ongoing battle for civil rights, which was still raging in 1967, despite the passage of the Civil Rights Act of 1964. This was one of the first times in any major motion picture when a black man reacted to provocation from a white man in such a way."
"Referring to the scene Poitier said, "[The scene] was almost not there. I said, 'I'll tell you what, I'll make this movie for you if you give me your absolute guarantee when he slaps me I slap him right back and you guarantee that it will play in every version of this movie.' I try not to do things that are against nature." However, Poitier's version of the story is contradicted by Mark Harris in his book, Pictures at a Revolution. Harris states that copies of the original draft of the screenplay that he obtained clearly contain the scene as filmed, which is backed up by Jewison and Silliphant."