Thion was the subject of some controversy when he wrote that "genocide" was, technically, not a proper description of what happened in Cambodia during the Khmer Rouge rule, because it was not a type (or an attempt) of killing based on purely ethnic grounds.
[citation needed] According to Thion:The reality is that genocide, massacres, wiping out entire peoples or cultures, and other inhuman atrocities, torture, massive corruption, and so on, are part and parcel of government policies, most usually applied to foreign countries.
If we want to change this situation, we must reform our own laws first, strip the authorities of their political immunity, abolish the "Reason of State" and the system of official secrecy which covers up all these crimes.
I am also fully in favour of a trial of Pol Pot and of his accomplices and his foreign associates, including American, Thai and Chinese officials who conspired to support him when he was in power and after his fall.
He criticized the prosecution of Robert Faurisson for Holocaust denial, and cast doubt on the accuracy of Filip Müller's book Eyewitness Auschwitz.