You should be respectful of other people's musical taste.
Barbara's cousin lets her listen to a song that her cousin likes and asks her what she thinks of it.
Barbara  wants to give her opinion of the song.
Barbara says that while the song may not be her cup of tea everybody has a unique taste in music.
Barbara tells her cousin that the song is garbage and that only dummies would like that sort of thing.
Barbara's cousin is happy that Barbara can be open minded to other people's taste.
Barbara's cousin is offended by her disrespectful comment and leaves.