Watch the older one done by the BBC, they have interviews of survivors and guards. One quote that stands out, from a guard interview, and makes you realize how much they BELIEVED in what they were doing, was " I would do it again. What we did was right, it was necessary. " holy shit man. This was years later. He was convinced. Shocking what you can make people believe in and they do some pretty hideous things. Don't watch with hate, don't watch with sorrow. Watch with absolute attention. Soak that shit into your mind so you never forget. You can hate and be sad when it's over but dont let the emotions keep you from getting all of the info. It's extremely important you know these things intimately, the how and why and the results, true human evil and true human perseverance. Know them both. History seems to repeat. Don't let it in your lifetime.
Read about the rape of Nanking as well. Another show of what "humanity" is capable of given the right circumstances.