This film's depiction of the early 1960s
Until recently the 1950s and early 1960s was always displayed in Hollywood movies as a nostalgic, carefree, safer and more innocent time.
Since the rise of the Progressive Left the new trend is to show that time period as an oppressive dystopia full of injustices and evil, as featured in this film. In fact, Leftist movie-makers and authors tend to present ANY past time period as being hideous and unliveable. For the Left, the only happiness is allowed in stories with a current time period.
Leftist artists HAVE to present the past in this negative way. Any attempt to show the past as pleasant would highlight the fact that 50+ years of strong Liberal influence on Western culture have turned us into a very horrifying and chaotic place with rampant poverty, crime, drugs and disorder.
They must portray the past as hellish to make the modern chaos they created look pleasant by contrast.