Instead of reflecting on the Good and Evil, I’d rather call out two technical aspects of the film that appeal to me.
First, the cinematography: (1) the unsettling optical aperture effect of the beginning (suggesting police work---and Johnny’s existence---“in the eyes of the public”?). (2) The cold, damp ambient worthy of Antonioni (“Blow-Up”): that long, speechless observation of frenzied parents picking up schoolchildren. (3) Painterly quality: after Johnny is taken away, his wife sitting alone, against windows opening to a balcony above which the lead-grey sky is strangely illuminated with surreal, apocalyptical light. Worthy of Munch.
Second, the speech. Compare Baxter in interrogation and Johnny at home. Johnny’s talk with his wife: bitter, despairing, embattled, impotent, often cut short by the speaker’s own recognition of its futility, his speech is half Pinter and half Shakespeare. Baxter, on the other hand, is a very articulate Satan (no wonder Bannen got an Oscar). He’s clever, nonchapant, gleeful --in turn with vulgar innuendos and subtle sophism; just the sort a brute like Johnny would want to exterminate/ worship. Baxter is everything that Johnny is not, for he’s not shakled by residual humanity as Johnny has been.
Apart from the visual/literal accomplishments, Lumet’s “Offence” can be read as a Nietschien characterization of evil: “When you stare into an abyss for a long time, the abyss also stares into you”. One is still tempted to ask, however, what is the point of all these raw, nervy torments?