I absolutely feel that museums should contain examples of such an important chapter in human history, and there should be specialized museums devoted exclusively to it. However, public outrage over the auction seems predicated on the idea that every last item connected with the internment should be catalogued and preserved in public museums, never allowed to be held in private collections. This naturally leads to the corollary that all history belongs in museums—and therefore a museum is the only place where a person can interact with history (safely segregated from the "real" world.)
The artifacts on display in publicly accesible museums represent a miniscule fraction of the world's history. They are actually a tiny fraction of even the select items owned by museums. For example, the Smithsonian displays items in thirteen showpiece museums sprawling over a mile of our nation's capital, yet all that space can still only show off less than two percent of their collection. The rest is shut away in storage, never seen by public eyes and in some cases not even properly maintained. Like waifs from an orphanage or puppies from a pound, many historical artifacts receive much better attention when they pass into private hands than when they were locked away in museum storage vaults.
Finite resources dictate that museums be extremely selective about what they preserve, let alone display. Archivists and museologists don't get paid to keep things: They get paid to decide what to throw away. Most museums can only afford to show the most significant examples of historical extremes, a "presidents and prostitutes" narrative of history. It is up to the rest of us to preserve the middle ground, the vast majority of our lives and heritage.
Every single person is a private collector of history, whether they realize it or not. Every item we own and interact with is a potential historic artifact. This applies to a bullet carried home from a Civil War battlefield by a much-lauded ancestor, or to a plastic fork brought home with last night's take-out dinner. Every item in life says something about the society which created it. Every single thing we use will tell a story about our values to future researchers.
The present is the past of the future. Imagine a reductio ad absurdum situation where no historical artifacts are allowed to remain in private ownership. At the end of every day, teams in white, full-body clean suits (like those used by forensics teams) sweep through every home in the world. They carefully pick up and carry away every single item, saying, "Today is over, so this important artifact now belongs to history. You can view it in our ever-expanding museum." Then they carry away the house too, since it is also a part of history. The whole scenario is like something out of the surrealist works of Samuel Beckett.
At what point does something cease being an item of everyday life and become a historic artifact worthy of preservation? Fresh fecal matter is distasteful, yet coprolites (the fossilized excrement of ancient creatures) have value to collectors—and they are displayed in museums. Age alone does not always make the distinction between discarded items and valued ones. I have viewed museum exhibits displaying items created within my own lifetime, and passed by trashbins stuffed with things that predated me substantially. Is it cultural importance and significance that makes the distinction? That argument would bring the decision back around to the "presidents and prostitutes" outlook on history.
Who decides what is truly significant in history, what is truly worth preserving? We all do. We are all part of history. How we choose to curate it will determine which artifacts we pass on to future generations.
 <http://www.si.edu/visit/maps> and <http://www.washingtonpost.com/wp-dyn/content/article/2011/01/28/AR2011012802985.html>
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