Filmmaker Spike Lee was elated when "BlacKkKlansman" was announced as the Oscar winner for Adapted Screenplay at the 91st Academy Awards. He urged people to be "on the right side of history".Lee paced towards the stage and hugged presenter Samuel L. Jackson in what was an effusive reaction to the award announcement.He paid a tribute to his grandmother -- whose mother was a slave -- and who lived to be 100 years old and was responsible for putting him through Morehouse College and New York University film school.Making a political comment, Lee, whose film takes on racism in the US, said: "The 2020 presidential election is around the corner. Let us all mobilise, let's all be on the right side of history. Make the moral choice between love versus hate."He received a standing ovation.Written by Charlie Wachtel and David Rabinowitz and Kevin Willmott and Spike Lee, the film is based on a book by Ron Stallworth.The crime drama is set in 1970s Colorado Springs, and follows the first African-American detective in the city's police department as he sets out to infiltrate and expose the local chapter of the Ku Klux Klan.Before the Adapted Screenplay honour, Nick Vallelonga, Brian Currie and Peter Farrelly won the Best Original Screenplay for "Green Book".The film is backed by Anil Ambani-led Reliance Entertainment.