Playing a villain can take a lot out of an actor. Tapping into the darkest parts of your mind can leave a mental mark when it’s a fictional character like the Joker, but what happens when the villain is real? This was the challenge facing Topher Grace, who plays KKK leader David Duke in Spike Lee’s latest film, BlackKKlansman.

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“I wish it was easy as the Joker,” says the former That '70s Show star, (who also played villain Eddie Broch in Spider-Man 3).  “The Joker is a fictional guy. That guy never existed. This is not only someone who’s real, but someone who I just watched in the Vice special on Charlottesville.”

Blackkklansman is based on the true story of officer Ron Stallworth, the first Black man to serve on the Colorado Springs police force and his infiltration of the Klu Klux Klan. John David Washington plays Stallworth, who had several phone conversations with members of the Klan, including Duke, over the course of his investigation.

“I had to do all of this research and kind of spend all this time thinking and researching David Duke,” says Grace. “And it was just overwhelmingly depressing. I read his autobiography, which is called My Awakening, it’s kind of like his Mein Kampf. I don’t usually get depressed at all by anything with acting, it’s all make believe—but this is not just a real-world figure, it’s close to some stuff that’s happening right now.”

Grace’s toughest time was with the language of hate used by Duke, particularly the N-word.

“It was the first time I’ve said it, period,” he says of the racially charged pejorative. “The night before I went to read for Spike—no one thought I was right to play the role—so I was happy to go in and kind of do a proof of concept and show Spike I think I can be that guy. So I’m alone in my office rehearsing the lines alone and I was swallowing the [bad] words. Wasn’t just the N-word, there were other words. The next day when I went in to see Spike I had a speech prepared where I said, 'I was uncomfortable with this dialogue.' But he immediately went to work on me and made me feel so comfortable that I got the role.”

Spike Lee drew from his experience working on past films to give Topher the confidence he needed.

“I said, 'Look man, go ahead.' And the reason why I said that is this happened before,” Lee explains.” My dear brother John Turturro, he was worried about his character in Do The Right Thing. He said, ‘Spike, I’m still riding the subway.’ But I think the audience is smart enough to know that they’re playing a part, and that’s not them. So I just had to make Topher a little at ease.”

While David Duke’s rhetoric is dangerous and incendiary, the take away for Grace was that he changed the face of racism in America, and that is what makes him so dangerous.

“The scary thing about David as a villain, and I mean this in real life and in the film, I guess, is that there was a common understanding of what a racist was previous to David in the '70s; it was like a redneck, beer belly guy. He put a different face on it. The most dangerous thing about him, and this was just confirmed by all my research, is that he’s really smart. Very charismatic. And that makes it more dangerous, because it speaks to more people. And I was just so thrilled that Spike had a script that connects [it all]. I mean, the first shot is the Civil War, and the last is Charlottesville in 2017. If you don’t study your history you’re doomed to repeat it.”

BlacKKKlansman is in theaters August 10.