...this immoral principle

Wretchard (Belmont Club) in discussing how deterrence works, and doesn't work, says,

What the GWOT did was deter the states which may have considered supplying al Qaeda-like organizations with the material for building nuclear weapons with the threat of collective responsibility. Deterrence has always, from its inception, been based on this immoral principle and it isn't necessary to approve to recognize it was the case.

Although the principle of collective responsibility can rankle, I'm now wondering just how moral or immoral it is. It certainly seems to be popular.

We've all been subject to collective responsibility. In the widest scale, whole ethnic groups have been the target of this kind of judgment. The notion that the white man is responsible for all the ills of the world is merely the latest incarnation. On the smallest scale, teachers and playground monitors who punish both participants in a fight, saying "I don't care who started it" are assigning collective responsibility.

On one hand, collective responsibility may be considered a "cop-out". It's used by people who can't be bothered to assess responsibility and properly assign blame. Instead, they take the lazy way out. In such a case, arguably it is an immoral policy.

On the other hand, what if the time and effort required to correctly assess responsibility and properly assign blame is so great that justice would not be perceived as being done. Making an entire school run laps during gym class to punish one or two unknown miscreants is heavy-handed, but perhaps less so than grilling kids until you finally isolate the culprits. You punish the whole class, and count on peers to "pay it forward" until the punishment reaches those who were responsible.

In a perfect world, it would be possible to isolate those who are responsible for any evil act and administer prompt and targeted punishment. This would be the perfectly moral approach.

In an imperfect world, we will be imperfectly moral. The trade-off here is, are we imperfectly moral in assigning collective responsibility, or are we imperfectly immoral in administering no punishment at all, and letting those wo do evil get away with it altogether?

It's a hard question to answer, and no one answer will serve for all cases.

For most of the Cold War, opposing nations held each other's civilian populations hostage.

And nuclear war never broke out, even when one of the opposing nations was in full collapse. The morality of holding all those people hostage has to be balanced, in a real world, against the morality of all those people not being turned to radioactive dust. It's a trade-off.