Sentimentalists beware: At some point, a sacred moment in time becomes a mere piece of history. For Germans, and their connection to the Third Reich, this phenomenon has been gradual, but the Holocaust may have finally devolved from the awe-inspiring to the banality of kitsch.

A new motion picture has opened in Germany, “Der Untergang” (“The Downfall”), which focuses on Adolf Hitler’s final days holed up in his Berlin bunker. Yet rather than portray him as murderous and psychotic – the standard casting call for the Fuehrer – the film allows Hitler to reveal a greater range of human complexity. Indeed, at times he is seen as tender, and even sympathetic.

For a country that continues to outlaw displays of Nazism, and where “Mein Kampf” remains contraband, the idea of humanizing Hitler beyond the image of an unredemptive monster has provoked renewed debate among Germans regarding the sanctity of their worst nightmare – particularly today, the 66th anniversary of Kristallnacht.

But there is more. This upcoming April, to commemorate the 60th anniversary of the liberation of Buchenwald, the gift shop at the concentration camp will begin selling souvenirs. Thankfully, nothing grotesque will go on sale, but the result is trivializing nonetheless. Some of the items include a small booklet of black-and-white photographs, plaques, wristbands, a button pin, and a potted plant of beech-tree sprigs. Not long ago, there would have been outcries of crassness had death camps gone commercial. Yet today, 60 years later, the reaction is more mixed and muted. Germany is opening itself up to new possibilities on how to comprehend its past.

There is a disturbing lesson in all this. No matter the magnitude of tragedy or the enormity of loss, we all must face the fact that historical distance has a way of liberating old pieties. Even mass murder is not immune. Over time what was once sacrosanct suddenly becomes commonplace; the kid gloves come off and with the blink of an eye our vision is turned from sentimental to bloodshot. We begin to find humor in the tragic, and flock to purchase commercial trinkets as artifacts of our languid memories.

Regrettably, there is no Scotchgard for this condition, no protective force field, no insulation from the insult.

Apparently, the burdens of history are easier to shoulder the deeper an event recedes into, well, history. Time withdraws, and so do we. And the further we advance, the less intimate become our memories, and our manners.

It is in this way that history has an entirely different agenda from memory. The priorities are almost in opposition. History is academic; memory is moral. The study of history improves with age, while memory fears the very thing that is lost with time. History benefits from dispassion, yet memory depends on emotion as the antidote to our indifference. Most of all, memory takes everything personally.

Who would have thought that Hitler could be seen by Germans as anything other than subhuman, a demonic mutation from an otherwise honorable gene pool? Once the object of national embarrassment and satiric ridicule, now, seemingly, Hitler is cinematically rewarded with a flesh-and-blood portrait – a man with considerable warts, yet ultimately not without his humanity. And how did it come to pass that even tasteful mementos of mass murder would be for sale at the very scene of the crime? Don’t our tragedies deserve more respect; are not our memories entitled to both untampered images and sacred grounds?

We should not be desecrating our tragedies by seeking to sanitize them. The impulse is understandable – the selfish desire to feel better about ourselves and our humanity. One grotesque expression of this – common in this morally relativistic age – is to conclude that Hitler, perhaps, was not such a bad guy after all. And upon departing from one of his death camps, what would be more reassuring and sanguine than to walk away with a potted plant as souvenir.

There is a cautionary note here for New Yorkers and the survivors and surviving families of the September 11 terrorist attacks. We just marked the third-year anniversary of the tragedy. The emotions are still very raw, which was evidenced in the conflict about how to memorialize the actual site without violating the unmarked graves. Some of the competing designs for the September 11 Memorial possessed more whistles and bells, yet the winning entry was praised for being more respectful and austere.

On some basic level, it comes down to the imperatives of memory, and its inevitable pieties. Is Ground Zero hallowed ground, or merely public space? Should we be showcasing the future, or finding ways to appropriately mourn the past? One day, no doubt, there will be a feature film in which Osama bin Laden is depicted as a warm, sensitive, caring soul. Don’t laugh. The other day, I watched a television ad where you can now purchase a September 11 memento, consisting of incinerated World Trade Center steel. And stay tuned, ABC and NBC have announced plans to produce September 11-related mini-series dramas.

Sadly, the shelf life on September 11 sacredness may have already expired.

Mr. Rosenbaum, a novelist and law professor, is the author of, “The Golems of Gotham,” and most recently, “The Myth of Moral Justice: Why Our Legal System Fails to Do What’s Right.”