Why is it acceptable to buy a Trapdoor Springfield when it could have been used to genocide the natives? Why is it acceptable to buy a Krag knowing it could have been used to murder Filipinos? Why is it acceptable to buy Lee Enfields knowing that they could have been used to kill the Boers? Why is it acceptable to buy a Japaneserifle, knowing it could be complicit in all the atrocities they committed in WWII. Why is it acceptable to buy a M1 Garand when it could have been used to commit war crimes in WWII (or anywhere it served afterwards)? Why is it acceptable to buy a Vietnam M16
parts kit knowing it could have been used in the My Lai Massacre or any other atrocity committed by the Americans in Vietnam?
Everyone, and I repeat EVERYONE has some darkness to their nations history. Pretending that you don't is a ignorant thing to do. Some were more overt than others, but ultimately everyone has some sort of dark tale, its a factor of us all being human.
Collecting takes many forms. People might collect Nazi items to remind us of the atrocities they committed. They might collect it because they are interested in that history (it is a fascinating time period/subject, if it wasn't there wouldn't be so many books/shows/movies, etc. on it). People might collect it because they are interested in the arms development. And I am sure there is tons of other reasons as to why they might collect Nazi items.
Personally my collection is mainly Swissand WWI era Bulgarian. Why? I like the Swiss craftsmanship and their history. I also like WWI Bulgarian history as they played a large part in WWI which is often forgotten. Recently I have been thinking of collecting action types. Why? Because recently I have been getting more interested in the quality of the manufacturing/design of firearms and variety is the spice of life. Ultimately I don't have to justify why I collect what I collect to anyone. Its a personal decision. If they don't like the type of stuff I collect, that's too bad. I don't tell others what to own, just as they don't get to tell me what to own.