Kendrick Lamar, the US music star and Pulitzer prize winner, halted a recent gig to call out a white fan for rapping the "n-word" from his own lyrics.
The woman, who gave her name only as Delaney, was one of several fans reportedly called on stage to perform Lamar's 2012 hit "M.A.A.D City" at the Hangout Festival in Alabama on Sunday.
But Delaney failed to self-censor and repeated several times the "n-word" from the lyrics to the song.
The word, while co-opted by black artists, remains the most derogatory term in the United States to refer to African Americans. Uttering it is a taboo for white people.
"Wait, wait, wait, wait, wait," said 30-year-old Lamar, who comes from the historically deprived Los Angeles community of Compton, cutting her off and stopping the music. The fan was initially baffled.
"Am I not cool enough for you? What's up, bro?" Delaney said.
"You gotta bleep one single word though," Lamar replied.
As realisation dawned, she apologized, saying, "Oh, I'm sorry. Did I do it?"
"Yeah you did it," Lamar said. He asked the audience whether she should remain on stage. They yelled back no, but Billboard magazine reported that Lamar allowed her to perform the song once again, anyway, this time without the slur.
The incident provoked a storm of reactions on social media, spotlighting America's continuing struggle with racism and the controversy surrounding the word.
"#KendrickLamar is BLACK, he can say, write and rap the n-word. The girl is WHITE, that word should never leave her mouth," tweeted one woman from Wyoming, Michigan under the handle @Michele11Amber.
"It's not that hard to keep that word out of your mouth. She knew better and she deserved to get called out."
"If you're white don't verbalize the N-word. This is a very simple rule we all collectively agreed to in the 1960s. Racists need to stop turning this into a debate," tweeted Alex Biancardi, who identifies as a student in California.
But while many commentators approved of Lamar's decision to cut off his fan, others were scathing.
"This is such a joke. If you feel so disrespected by someone rapping the words to the song you wrote and you invited a WHITE GIRL onstage, then don't write the lyrics," tweeted a woman called Taylor Orton.
In April, Lamar became the first rapper to win a Pulitzer prize for music, with the board citing his skill in telling the African American experience.
He won for the album "DAMN.," which the board called "a virtuosic song collection unified by its vernacular authenticity and rhythmic dynamism that offers affecting vignettes capturing the complexity of modern African American life."
