The audience for the most part did not pursue this point, and this was a lost opportunity. The implications of Derrida's observation run, fascinatingly, in two different directions. Punishment is customarily defined as hard treatment imposed because of a violation of legal rules. Capital punishment has been justified on the ground that it is cathartic for the victim's family. If so, then this reason cannot be a justification for punishment.
Punishment is the infliction of pain for good reasons.
It may be that execution, being cruel, can never be a genuine punishment. The issue of capital punishment in the Western philosophical tradition received greater attention. Derrida began with the surprising but true observation that no philosopher in the Western tradition argues against the death penalty, while many of the most prominent, notably Immanuel Kant, advance arguments in favor of it. Prof. Scott Shapiro picked up this point, suggesting that the reason is the difficulty in distinguishing logically between death and other punishments. These are not the kind of arguments that philosophers make.