The star hit headlines back in September when he walked out of an interview promoting the flick after the journalist asked if he's concerned the film may "inspire" violence.
While, at the time, he claimed he "doesn't think it's the responsibility of a filmmaker to teach the audience morality or the difference between right or wrong", the actor, who plays DC Comics villain Arthur Fleck in the movie, has since confessed onscreen violence is "part of the problem".
"It was an awkward position to be in because I thought, 'Well, I can't address this because this is the thing that is potentially part of the problem – that's precisely what you shouldn't do'," he told the Los Angeles Times newspaper. "So it suddenly seemed like I was being evasive and trying to avoid this topic because it made me uncomfortable."
"But really I was thinking, 'This is the very thing that would excite this kind of personality.'"
The movie went on to become the most successful R-rated film of all time but has not been without its controversy, particularly as Phoenix's disturbed character kicks off a cycle of violence after getting hold of a gun.
Before its release, Warner Bros. bosses opted not to show the film at the Cinemark Aurora theatre in Colorado, where 12 people were killed during a screening of Batman movie "The Dark Knight Rises" in 2012, when a gunman opened fire during a late-night showing.
The decision came following the publication of an open letter from the families of four Aurora shooting victims to studio CEO and chairperson Ann Sarnoff in the Hollywood trade papers, in which they expressed their concern about the release of "Joker".