Gruen held many teaching posts, including seventeen years as professor of psychology at Rutgers University.

According to Sigmund Freud, human beings are born with an innate tendency to destruction and violence; throughout his scholarly and clinical career, Prof. Gruen challenged that assumption, arguing instead that at the root of evil lies self-hatred, a rage originating in a self-betrayal that begins in childhood, when autonomy is surrendered in exchange for the "love" of those who wield power over us.

Gruen traced this pattern of over-adaptation, and the fate of those who resist the pressure to conform, through a number of case studies, sociological phenomena—from Nazism to Reaganomics—and literary works.

The insanity of rage and numbness that this hyper-conformity produces, unfortunately, goes widely unrecognized precisely because it has become the cold, tough "realism" that modern society inculcates into its members and even admires.

His elegant and far-reaching conclusion, elaborated in the books and essays listed below, is that while autonomy and authenticity are not easily attained, their absence proves catastrophic to both the individual and society as the embittered conformists seek new victims on whom to wreak violence and avenge their psychic wounds.