The way I see it:
We killed them, now we get to keep their shit as souvenirs. The spoils of war and all that. I own an Austrian rifle from WWI that was pressed into service in WWII. It has Nazi markings stamped on the stock and the original ammunition it came with has Nazi markings on it. Are these objects inherently evil? No. Am I a naughty, naughty person for keeping them? No (although my naughtiness is debatable). Do I sympathize with Nazis? Make that one a hell no.
Also, slightly off topic, but it sortof illustrates my point… a friend of mine knew an old man who served as a US GI in Europe during WWII. Every day after the war, he would wear a former Nazi cap, kind of like this one. One day, he was out grocery shopping when a guy about my age came up to him and basically called him a Nazi after telling him to take off the hat. Old man basically told the kid that he earned the right to wear that hat after he personally took it off the previous owner who didn’t need it anymore. (Because he shot his Nazi ass)
Furthermore, would I buy Nazi paraphernalia? Depends on what it was. I’d love to have Does this make me a Nazi sympathizer? No. Does it mean I support Nazi ideology? Hardly.