The culminating scenes of the Unite the Right march, the murder of counter-demonstrator Heather Heyer – to whom the film is dedicated – and the clips of Trump did not exist when he began filming. "But it had to end in the present day. A Spike Lee Joint has got to flow, got to not be rigid, got to be on it." Lee is in full flow now. He doesn't care what the critics say! "I know we're on the right side of history." And in case anyone had forgotten their history: "The US was built on genocide and slavery; that is the fabric of America!"

Yes, he says next day in our first interview, he intended to kick-start controversy. And it worked. Sure did! "Did you see the papers? Did you see CNN last night? He whoops. "They had on the whole press conference! They showed the trailer! So that's good. I'm happy!"

There was a time when Lee never seemed happy, at least not in public and certainly not with white folks. "Here we are in the south of France," he says later, as we sit on a couch in one of the restaurants on the beach. "I have been here many times and it's always been a pleasure to me." Now, this just isn't true. In 1989 he stormed out in high dudgeon when the much-admired Do The Right Thing lost out on the top prize, the Palme D'Or, to Steven Soderbergh's​ debut Sex, Lies, and Videotape. Lee blamed his defeat on that year's jury president, Wim Wenders. "Somewhere deep in my closet I have a Louisville Slugger bat with Wenders' name on it," he said. (He has since repudiated this remark as "immature" but, according to a recent interview, still holds a grudge.)

In 1991 he came back to Cannes with Jungle Fever; he returned again with Girl 6 out of competition in 1996 and again with the brilliant Summer of Sam, relegated to the sidebar (and often more interesting) Directors' Fortnight in 1999. Whatever he says now, he never seemed happy. Shelton Jackson Lee, whose earned his nickname as "a tough baby" from his mother, had a reputation as the hardest interviewee in town, known for following sneering one-word answers with silences where his expression said nothing so much as "Go on, try and impress me".

I know I didn't impress him. Remember when you wouldn't say anything to people like me, Spike? "Well, that was a lo-oooonnng time ago," he says, letting rip with one of his great barking laughs. We have already had a chuckle about how old we are – he's 61 – and how long we have been in our respective games. "Hopefully you get smarter as you get older."

Things have changed, certainly. He has insisted on holding my voice recorder and is sitting squeezed up so close to me we could sing a duet into it. It's disconcerting, but I don't care; he's talking. Admittedly, some of that talk consists of apparently rehearsed performances. I don't really mind that either.

"Coming here, I knew I'd be asked by journalists like yourself, esteemed journalists from all over the world, 'Spike, what do you see? Can you see where we are in the world today?'" he booms, holding the recorder like a microphone as he turns to an imaginary audience. "Being a cinephile, I started to think of a film title and I came up with a film I like very much and a director I respect very much, Peter Weir. And the title is, The Year of Living Dangerously."

I've already heard him give this little speech twice, but he isn't bothered about that; I suspect he works on the preacher's principle that if you keep saying something, it might just register. He drops his voice and turns to me. "Is he Australian?" Yes. "Is he still alive?" Yes, I assure him. We return to the room. "Shout out to my man, Peter Weir! You inspired me! You had the crystal ball! We are actually living in that year of living dangerously!" I ask if he has seen Weir's early feature, rarely seen outside Australia, The Cars that Ate Paris, because he has spoken the truth about one thing: Lee is a formidable cinephile with a shot-by-shot knowledge of film history. He brightens and promises to find it. "I'm going to check it out, Peter!" he yells at the space in front of us. "Now you hit me to it, I'm going to get on it!"

My thing is I want to keep getting better at my craft. Keep getting better at storytelling.

BlacKkKlansman follows much the same principle as Lee's declamatory speeches: keep telling people something and maybe they'll get it. The artfulness of his scenic composition and feel for rhythm, informed by his film scholarship – even his first feature, the sex comedy She's Gotta Have It (1986), he said was primarily inspired by Kurosawa's Rashomon – is always dazzling, but nobody could accuse BlacKkKlansman of subtlety. Racist characters constantly tell each other how very racist they are in repulsive language that, I would guess, was very hard for the actors to say. Lee shrugs. "We are in pursuit of the truth." But in my experience, racist talk is usually more slippery than that. "Honest, that's the way they speak," he insists. "I don't tell those guys [in Virginia] to chant 'Jews will not replace us'! I didn't tell those terrorists to chant 'Blood and soil!' They did that themselves."

Lee has never been inclined to take a step backwards; arguably, we might never have heard of him if he had. Having successfully applied from a black college to do graduate film studies at New York University – "they said I was crazy" – he soon found himself on the cultural frontline, arguing in class that they couldn't just swallow the axiomatic greatness of D. W. Griffith's The Birth of a Nation (1915) without discussing the fact that the film was "used as a recruiting tool for the Klan. People got killed because of that film." His response was to make his first student film about a black screenwriter attacked by the Klan, complete with burning crosses, when he refuses to do the script for a Birth of a Nation remake. This apostasy so offended his teachers that he came close to being asked to leave. So there has been some progress, in fact; Lee is now a tenured professor at NYU.

What that first fight about an iconic silent film showed him, apart from confirming his conviction that racism was knitted into American culture, was that cinema was demonstrably powerful, whether or not that power was used for good. "I will go to my grave believing art can change the world," he says. "There is a reason why President Woodrow Wilson said, when they showed The Birth of a Nation in the White House, that it was 'like writing history with lightning'. That is the power of film!

"And here is something I would like to say. The reason the United States is the power it is – although that is slipping – is not because we had nuclear arms before anyone else, but because of culture. That's how we dominate the world. Levis! Rock and roll! Hip hop! Nike! A nuclear bomb is not going to alter the way somebody dresses, walks, talks or dances. It's American culture that does that."

Underwritten, I suggest, by those bombs and quite a few wars. "But there is great stuff! There are great films! Music – forget about it! Ain't nobody gonna f--- with us when it comes to music." He explodes into another laugh. "But like you said, McDonalds. So there's bad stuff too." His dream project of the moment, he says, is to make his second film School Daze into a Broadway musical. "Hopefully I'll get to it in 2019. A full Jerome Robbins, Bob Fosse, singing and dancing Broadway musical! The great white way!"

And what else does he want to get done? "Onward and upward!" he hoots. "My thing is I want to keep getting better at my craft. Keep getting better at storytelling." Keep getting better? Lee has been making feature films, along with shorts and documentaries, for a bit over 30 years. It strikes me that he probably sees himself as mid-career and, given that everyone says he is always the most energetic person on set and works astonishingly long hours, he may well be. In the last couple of years, he has directed two stage plays as television specials and turned She's Gotta Have It into a 10-episode series, along with steering BlacKkKlansman to Cannes. A Marvel film is the next thing on his slate. Plus he's fired up with anger; he may be friendly in a way he never used to be, but there is just so much to be angry about. Shout out to Spike Lee! He's not going to let the fight go now.

BlacKkKlansman is screening at the Sydney Film Festival June 16 and 17, and releases in Australian cinemas on August 16.