Did you know that animal-loving British families killed an estimated 400,000 household pets—cats and dogs—in the first week after Great Britain declared war on Germany in September, 1939? Neither did I, and now a new book by Hilda Kean, “The Great Dog and Cat Massacre,” sets out to remind us of that ugly episode.

As the New York Times review of the book notes and Kean explains, the mass euthanasia was “publicly lamented at the time,” but has since been erased from memory.  But why has it been erased from memory, and how? This is a disturbing cultural phenomenon that Ethics Alarms has covered before, notably in the post about dance marathons in the U.S. during the Depression. One of the definitions of culture is what we choose to remember and what we choose to forget. Forgetting, however, while often psychically soothing and an easy way to avoid guilt and accountability, is a pre-unethical condition. That which has been forgotten can no longer teach us, and a society that collectively decides to pretend something cruel, horrible or traumatic didn’t happen risks allowing it to happen again.

This, of course, is one more reason why the recent progressive mania for historical airbrushing is dangerous, irresponsible and unethical. Keep that statue of “Joe Pa” on the Penn State campus. Leave  King Andy on the twenty dollar bill.  Don’t take down that bust of Bill Cosby in the TV Hall of Fame. All civilizations have fallen heroes, moments of panic, times when they forget their values and betray their aspirations. Of course it is painful and embarrassing to remember these things, but also essential if human ethics are going to progress instead of stagnating, or even going backwards. We associate the elimination of cultural memories with totalitarian regimes, and for good reason, for they are blatant and shameless about it.

No nation is immune from the process’s appeal, however. When I was going to grade school and studying the Presidents of the United States, Jackson and Woodrow Wilson were routinely hailed by (mostly Democratic) historians as among the greatest of the great. The first Jackson biography I read barely mentioned the Trail of Tears. I read four well-regarded biographies of Wilson that ignored his support for Jim Crow, and the degree to which he deliberated reversed advances in civil rights, being an unapologetic white supremacist. The influenza epidemic that killed millions was excised from my school’s history books. Thomas Jefferson’s concubine, Sally Hemmings? Who?

Just as the Rape of Nanking and Japan’s forced prostitution of Korean women is still censored in Japan’s history courses, the Machiavellian roots of the Mexican War was largely absent from ours for more than a century. In Massachusetts schools we were shown the frightening photographs of what the cruel Confederates did to Union soldiers at the Andersonville prison camp, but nobody mentioned the  North’s prison camp for Confederate prisoners in Elmira, New York, where conditions were as bad or worse.  Did any of your teachers discuss Abraham Lincoln’s order to hang thirty-eight Dakota Indians, in the largest mass execution in US history?  Did they teach you about the 1923 Rosewood Massacre?

Historians like Hilda Kean perform a great service by reviving the disturbing memories that cultures try to excise, even as they make the task of evaluating our past and the actions of past leaders and luminaries more difficult. Nevertheless, confronting the truth is far safer than burying it, hiding it, or pretending that it doesn’t exist.