BlacKkKlansman is set in 1970s Colorado about the Ku Klux Klan about the deadly racism that is still prevalent in the United States. It is based on the true story of Ron Stallworth, a black police officer who infiltrated the Colorado Springs chapter of the KKK and stars John David Washington, son of Denzel, and Adam Driver who plays the white officer who helps him pull off the subterfuge.
At the post screening news conference, Lee spoke of the far-right rally in Charlottesville, Virginia last August where counter-protester Heather Heyer was killed, and clips of President Donald Trump blaming "both sides" for the violence.
"That motherf***er was given a chance to say 'We are about love and not hate'," he said.
"And that motherf***er did not denounce the motherf***ing Klan, the alt-right, and those Nazi motherf***ers. It was a defining moment and he could have said to the world, not the United States, that we were better than that."
"This film to me is a wake-up call, we've gone for the "okey-doke", walking around in a daze, and stuff is happening and it's topsy-turvy and fake has been trumpeted as truth.
"That's what this film is about and I know in my heart, I don't care what the critics say or anybody else, we are on the right side of history with this film." He said.
The film has gone down well with critics at Cannes. According to reports, the audience gave the film a six-minute standing ovation at the end of the screening.