I generally think it's important to educate yourself about horrible acts in human history so you can better do your small part to prevent their repetition, so I've seen some fairly disturbing movies and documentaries. Taxi to the Dark Side beats them all. My country did it during my adult life.
You really need to watch this movie. A version of the film edited down by 20 minutes for the BBC is available on google video, but ignore the first 35 seconds by the person who posted it.