It seems to me the question of “not knowing” or “knowing” about a society-wide horror is not simple binary. It is possible to know enough to want not to know more; and it is possible to cordon off and neutralize the knowledge you do have. There are two walls that help with the compartmentalization. First is the wall that is erected by Authority; you “know” what “goes on” in that windowless building with the strange smell, but you are not seeing it. This wall is made of wood, wires, bricks. The second wall is psychological and erected by the individual in collusion with Authority. You do not allow the persistence of the horror to interfere with your daily life; the knowledge dulls itself, like an odor. If a few facts find their way to you, you tell yourself they are exaggerated, and above all, you do not investigate further, you do not ask certain questions when you know the answers will ruin your dinner. It is easier to compartmentalize the idea of the horror than its lived details; this is why stories hit us harder than statistics.
I myself “knew” about the condition of animals on factory farms, but I used all the psychological means at my disposal not to be troubled by it, until quite recently (under pressure from my wife). The more I’ve thought about my own mechanisms of unknowing, the more I’ve recalled the accounts I’ve recently read about the attitude of “decent” Germans toward the concentration camps. I don’t mean this to be a polemical or strident analogy comparing factory farms and death factories. That analogy would require an attribution of equal value to human life and animal life that we find only in Jain and Hindu mystics (and, it seems, animal rights activists). Though it might as well be noted here that the actual details—the mass transport and overcrowding of victims in disease and filth; the public’s being denied access; the efficiency-maximized killing—are already in place. Consider: Albert Speer recounted how he was told about Auschwitz by a friend who visited it. The friend, visibly shaken up, told him never to go there, that is, never to acquire the knowledge of what was happening. To keep the horror behind its physical barrier so that the physical concealment could continue to reinforce the psychological one. Most Americans know what happens to animals in factory farms; if forced to face the details, they would find the details horrifying; they know they would find the details horrifying; the majority of us (myself included until recently) live comfortably with the system anyway. Based on the accounts I’ve read, it seems that a very similar (if not identical) combination of psychological mechanisms reconciled the majority of German citizens to what was happening to the Jews. Nazi propaganda frequently equated racial minorities with animals in order to facilitate this.
It would seem the only thing more dangerous than being equated with an animal is being an animal. After a couple movies and a book about factory farming, I can report that I have sworn off the hormonally and genetically modified monstered-up meatlike substance we call meat forever. Pass the broccoli.