“The common good” (or “the public interest”) is an undefined and undefinable concept: there is no such entity as “the tribe” or “the public”; the tribe (or the public or society) is only a number of individual men. Nothing can be good for the tribe as such; “good” and “value” pertain only to a living organism—to an individual living organism—not to a disembodied aggregate of relationships.
When “the common good” of a society is regarded as something apart from and superior to the individual good of its members, it means that the good of some men takes precedence over the good of others, with those others consigned to the status of sacrificial animals. What makes the victims accept it, and permit a society to perpetrate a moral atrocity of that kind?
The answer lies in philosophy. In philosophical theories on the nature of moral values.