Director Lee Daniels tried to push the star, who plays prisoner John Cusack's lover in the upcoming movie, into sticking to the script and using the derogatory term ""n**ger"" as it seemed appropriate for her trashy character.
However, the Oscar winner drew the line and the two became embroiled in a heated argument over her strict stance - and now Kidman reveals it was all to avoid offending her teenage son and his culture.
At a press conference for the film, she told reporters, ""I have a son who is African American. I just didn't feel like it was right.""
And Kidman hopes Daniels understands she wasn't trying to be rude by defying his wishes.
She added, ""What I try to do as an actor is fulfil a directors vision. I have opinions, but at the same time I'm not there to stop him from anything. I've really tried to do that in every film. I never want to pull them off their vision.""
And Daniels tells WENN his producers urged him not to push Kidman too far on the script slur - because she was really taking risks in other parts of the movie.
He explains, ""They said I shouldn't complain because my producer said, ""Day one she was bent over having sex on a washing machine with John Cusack. (On) day two she urinates on Zac Efron and (on) day three she has telepathic sex, so I think you could forgive her for the N word'.""