Not necessary, because how citizens “view justice” is irrelevant to the reasoning. What matters is whether citizens are able to criticize the people involved in determing the punishment of criminals. Citizens’ views about justice have no clear relationship to their ability to criticize.

Not necessary, because we already have a premise that tells us what’s required for justice — citizens have to be able to criticize people involved in determining the punishment of criminals. The author believes we don’t meet that requirement. Some entirely separate requirement related to considering the effect of punishment is not part of what the author views as necessary for justice.

Not necessary, because the argument reasons by trying to show that we don’t meet what’s required in order to ensure justice in the legal system. Whether a legal system has as its primary purpose the goal of justice is separate from whether the system in fact administers justice. The argument is concerned with whether justice actually is ensured in the legal system, not with the purpose of the system.

Not necessary, because even if a concern for punishment is compatible with an emphasis on deterrence, that doesn’t change the fact that experts are involved in determining punishment, and citizens can still lack the ability to criticize those experts. The argument’s reasoning is not based on incompatibility of various goals of the legal system; it’s based on citizens’ inability to criticize certain people.

Necessary, because if it were not true — if citizens without knowledge about how punishments affect criminals ARE CAPABLE of criticizing experts in that area — then we have no reason to think citizens are unable to criticize the people involved in determining punishment. And then we have no reason to think we don’t meet what’s required in order to ensure justice in the legal system.