It's rude to negatively comment on someone's look.
Ron is sitting and having dinner with Sammy, when they see a relatively ugly woman walk by.
Ron wants to make Sammy laugh.
Ron tells a funny joke he heard on Reddit the other day.
Ron comes up with a pretty witty comment on the girl's looks.
Sammy laughs, and as the woman hears the end of the joke, knows he's laughing at the joke.
Sammy laughs and the woman knows they're laughing at her, and gets hurt.