And I'd really like you to stop harping on the 'fetish porn' bit. It's deeply irrelevant. The important part is the 'Nazi' bit.
No, it's fully relevant. Because as you say, they could just be peddling war movies. Triumph of the Will, despicable as it's intention could be, is still a piece of history both as a record and point of perspective.
Pornography made in the 2000's, with people wearing Nazi uniforms has no historical relevance.
If the vendor's only purpose is to be a source of war movies and historical documents, why would they have Nazi fetish porn?
Because porn sells? Seriously, branching out from war movies to porn isn't exactly the greatest leap ever. It's the Nazi bit that makes the whole thing problematic.