Collective punishments are part of "negative" incentives that are used to reduce crime, military aggression, and other injurious acts. There is often a strong case for such collective punishment to deter harmful acts. Punishing the individuals or groups who commit these acts through police, armed forces, and the judiciary is the first line of defense against such socially harmful behavior. Sometimes, in addition, "positive" incentives are used to encourage the help of private enforcers. This is accomplished by offering payments to whistleblowers who report white collar crime, to spies who give information on the military intentions of potential enemies, and to individuals who provide information on wanted criminals or unsolved crimes.
In his discussion in favor of collective punishment, Posner uses the example of employers who may be held liable for injuries due to acts by their employees while performing their duties. Employer punishment is often appropriate for the reasons Posner gives. A less good example frequently discussed is the owners of bars who are penalized for automobile accidents or other injuries caused by persons who became drunk at their bars. Similarly, some states hold the hosts of parties partly responsible for any automobile accidents or other injuries caused by guests who had too much to drink at their parties.
I believe that collective responsibility in these drunk-driving examples and in many other situations is inappropriate because those being punished have little ability to deter the injurious behavior that is being discouraged. Can party hosts be expected to keep track of how much each of their guests has drunk, especially at large cocktail parties? That seems to me to an unwise use of negative incentives unless the goal is to discourage cocktail parties themselves. Otherwise, it is best to only punish the individuals who get drunk at parties and afterwards injure others. They are the ones who can best keep track of how much they drink.
It is easier for managers of bars than party hosts to keep track of the number of drinks ordered by different patrons. However, punishments to bar owners after serving more than say 4 drinks to patrons who later commit acts that injure others would give heavy drinkers an incentive to bar hop, and have their quota of 4 drinks at each of several bars. That might cut down the amount of heavy drinking since bar hoping is more costly than drinking at a single bar, but it also punishes heavy drinkers who take care not to drive afterwards or engage in different actions that cause injury to others. It surely would not make much sense to collectively punish the set of bars where patrons accumulate their excessive amount of drinking. So my conclusion is that in this case too the preferable policy is to only punish intoxicated persons who cause injuries to others, and not attempt collective punishment of bar owners.
To take a different example, parents should often be held responsible for harms to others caused by their younger children. Parents can discourage crimes and other anti-social acts of these children by the upbringing they provide, and also by the punishments they administer to children who engage in such acts. Since after a certain age, perhaps sixteen or eighteen, parents have much less control over children, parental responsibility for children's acts should diminish, and children's responsibility should increase as the children age.
At one time, children were responsible after the death of parents for any debts their parents left. Children were also punished for other anti-social behavior of their parents. This type of collective punishment has been eliminated by developed nations, presumably because children do not have the power typically to deter their parents from contracting debts or committing crimes. The only justification for such collective punishment of children in these cases would be that parents care about the children, and that caring parents would be less likely to enter into debts they cannot pay, or engage in anti-social acts, if children were held responsible for parental behavior. But such collective punishment to children would have little effect on selfish parents, and it would increase the suffering of their children who already are harmed by having selfish parents.
To take a different political example than the Lebanese one that Posner uses, should the German people have been held collectively responsible for the atrocities committed by Hitler and other Nazis? It was inevitable that many German people suffered from World War II, although bombing of Dresden and some other cities by the Allies was probably unnecessary. Collective punishment of leading Nazis was appropriate, as was the requirement that Germany pay reparations for property taken, for some of the damages caused by German occupations of various countries, and for the murder of millions of Jews, Poles, Russians, and other groups.
However, it would be more far-fetched to hold the German people responsible for the election of Hitler since he took steps to prevent the German people from voting him out of office. Moreover, people who voted for Hitler in the first place could not have easily anticipated the full dimensions of the horrors he would inflict on the world.