There exists among the intolerably degraded the perverse and powerful desire to force into the arena of the actual the fantastic crimes of which they have been accused, achieving their vengeance and their own destruction through making the nightmare real.

Baldwin is describing a psychological and social dynamic in which people who have been relentlessly demeaned or scapegoated may come to internalize the accusations leveled against them. Under extreme degradation, the “fantastic crimes” imagined by their persecutors can become a script: the accused are tempted to enact the very nightmare projected onto them, both as a form of bitter retaliation and as a confirmation of the world’s expectations. The result is double-edged—vengeance against an oppressive order, but also self-destruction, since making the fantasy “real” tightens the trap of stigma and punishment. The line reads as an indictment of dehumanizing narratives that manufacture the behavior they claim merely to describe.