Gotham City in Joker is a fundamentally broken city.

• Arthur Fleck (the Joker) is failed by every level of society.
• However, every class in Joker wants to shift the blame.
• When Arthur commits murder, society turns this purposeless act of violence into an act of social rebellion.
• Despite knowing nothing about the reason for the murder, Gotham's people imbue it with shared meaning, forcing this event into their narrative, and held Joker as a hero.
• When Arthur commits another purposeless murder, it sparks riots.
• The real villain of the movie is the broader society that latches onto actions and imbues them with nonexistent meaning to justify their own crimes.

Joker is the most realistic depiction of group dynamics. The Joker has no plans, no real motives, no point to make, but is as much a victim of circumstances.

The Joker doesn't manipulate or use other people to achieve his ends. He has no ends to achieve, yet society romanticizes his purposeless actions.

Deindividuation is linked to everything from mass riots to lynch mobs. It shows the dangers of thinking that simple numbers can equate to moral action.

The shared identities of deindividuated groups - where there is a loss of self-awareness - can result in biased recollections and interpretations of events that can create horrendous violence.

We like simple, almost cartoonish, villains that we can point fingers at so we don't have to do any self-reflection or think about our own potential for immoral behavior.

Like the people of Gotham, we want to villainize those who disagree with us while excusing the behavior of our in-groups. This makes mass violence and individuation all the more likely.