Why is it only WWII (and specifically the Nazi aspects thereof) which is somehow considered bad from which to make a profit? Genocide and oppression of various cultural, ethnic and religious groups has been a repeated theme for centuries. Other than a difference in scale, why not the same attitude toward other genocidal acts? There certainly isn't any bias against profiting as a result of those periods in history.

The Khmer Rouge killed 1.5 million people out of a total of 7 million population. In just 100 days, over 500,000 persons were killed in Rwanda for their political beliefs. It is estimated that around 13 million native Americans were deliberately killed (as opposed to being "accidentally" killed by introduced diseases) during colonial and post-colonial periods. How many people have to die for it to be "bad" or do the other genocides not matter because they happened to non-Europeans and/or in third world countries?

Keeping reminders of evil doesn't seem to have much preventive value. When necessary, those in power conveniently "forget" history and continue on their chosen path, regardless of lessons that might be learned from the past. And many more blindly follow.