People are unjust to anger - it can be enlivening and a lot of fun.

The remark pushes back against the moral reflex that treats anger as merely corrosive or shameful. Roth suggests that anger can be a vitalizing force—an emotional stimulant that sharpens perception, energizes speech, and can even produce a perverse pleasure in confrontation or candor. Read in light of his fiction’s frequent interest in transgression and the unruly life of the psyche, the line implies that “negative” emotions may have legitimate uses: they can animate argument, fuel artistic intensity, and puncture complacency. At the same time, calling anger “fun” hints at its seductions and dangers—how easily righteous indignation can become self-indulgent entertainment.