The 24-year-old actor, who plays Krauss in the movie, said that after viewing the footage, he was scared to see how those groups believed they were right in oppressing people from other races, reported ContactMusic.
"I've received an education through making this film. I watched a lot of footage of KKK members and white supremacist groups for 'Detroit'.
"The scariest thing about them is that they're so righteous and convinced that they're doing right by continuing to oppress others. There's a racist rhetoric based on lies that has this brainwashing effect on them," Poulter told Shortlist magazine.
The Kathryn Bigelow-directed film tackles the events of the Detroit rebellion in July 1967, that was triggered by heavy-handed policing of the city's black population