In the documentary (in the form of cinéma vérité) The Act of Killing (1), the director learnt about "anti-communist" massacres in 1965 Indonesia, which was sanctioned by a regime whose successors were still in power in the modern times. He compared the atmosphere of the country as if he came to Germany 40 years after WW2, but with the Nazis having won it. He talks to some of the killers, and he found them not even regretful, but boastful - throughout the documentary, he learns that if they admitted they were wrong, they'd be having to admit to themselves that they murdered a lot of innocent people, so they'd rather construct a fantasy world where they're the good guys.

There's even a musical segment of the documentary (he convinced the people to reimagine their doings in the style of 50's Hollywood movies they loved) where actors playing the victims thank the killers for saving them from godlessness and sending them to heaven: https://www.youtube.com/watch?v=o-ta9To14yw

I wonder how many of the genocide-defenders and genocide-enablers (not to mention genocide-executioners) will have similar PTSD...

1) https://www.youtube.com/watch?v=4kJZb2Q1NmE