It is hard to explain. If the posters were official posters of the government (or from mainstream movies) then they reflect the country's attitude as a whole at that time. But when it is from hate groups or from Nazi Germany, then I mostly want nothing to do with it. The German programs are in German, and don't have offensive images, so they slide by.
I would auction a poster from a Hollywood movie that showed a lynching, but I would not run a poster from a hate group with the same image.
It is a personal choice. You can of course do as you wish, but I was explaining part of why you see so little of it.