Continuity mistake: When Joker is dancing on the stairs he throws his cigarette. Then when the cops arrive at the top of the stairs we see him blowing smoke from the same cigarette. Then the cigarette is gone again. (01:30:40)

Joker (2019)
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Directed by: Todd Phillips
Starring: Robert De Niro, Joaquin Phoenix, Frances Conroy, Zazie Beetz
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Arthur Fleck: My mother always tells me to smile and put on a happy face. She told me I had a purpose: to bring laughter and joy to the world.
Trivia: Towards the end while Joker is being transported in the police car, the shot of him through the window is similar to one of Heath Ledger's Joker in The Dark Knight.
Question: Why was this movie so controversial?
Answer: In a nutshell, it's because the film's protagonist is a mentally disturbed killer, and certain groups in America thought the film's violence would lead to copycat behavior.
I never got this aspect of the controversy, if anything, it goes to show what can happen when mental illness goes untreated.
I agree with you on that, but unfortunately, there's so many people, at least in the United States, that have no sense of nuance and are prone to knee-jerk reactions. They would rather condemn and blame different kinds of media for society's ills, rather than stop and look at the message something is trying to tell.
I read about the concern over possible copycat behavior in an on-line article; Phaneron's answer is correct.
Answer: Because the left thought it would encourage violence and mocked liberal run cities.The right thought the same on violence, it seemingly justified a mentally ill guy's actions, that it made white businessmen bad guys. Both sides in general only complained about Joker for attention.





Suggested correction: They purposely stuck the images in a way that it repeats itself over and over again. It's intentionally made in a way of not flowing straightforward.