Ok, so you may want to look at my answer here in regards to the terminology used to describe the Khmer Rouge regime’s time in power. While it has been somewhat normalised to refer to the 1975-1979 years of Pol Pot’s regime as ‘the Cambodian genocide’ this legal definition does not strictly apply to the overall ‘point’ of what the Cambodian communists were hoping to achieve.

Minority groups within DK did suffer disproportionately to the majority Khmer. The Khmer death rate is around 18%, while a group like the Cham is closer to 35%. The Vietnamese close to 100%. The Chinese death rate is thought to be around 50%.

So, why is this the case?

First of all I will address the question of the leadership’s ethnicity and the relationship between these conceptions of race and Khmer culture.

Here is a quote from Philip Short’s (quite excellent) biography of Pol Pot, titled… “Pol Pot”:

‘But race in Cambodia is determined by behaviour rather than blood line. Loth – or Phem Saloth as he later called himself (Pot’s father)… did not practise the Chinese rites. He and his wife did not sweep their ancestors’ graves at the Qingming festival, or celebrate the Chinese New Year. Nor did they speak Chinese. They lived as Khmers and therefore, racially, they were Khmer, in their own minds as well as those of their neighbours.’

That gives you a sense of how these ideas of ethnicity were often translated in Cambodia. Take for example the pseudonym that Sar used when penning his first communist article while studying in Paris – Khmer Daeum – ‘old Khmer’, emphasising the fact that Sar himself did not acknowledge any links to his distant Chinese ancestry. I can’t say I have enough information on the other leaders to suggest that they had similar ideas but I hope that through showing Pot’s attitude toward this that we can maybe suggest the lower rungs of the leadership had similar notions.

The sort of, inner circle of the leadership, was of a semi-elite background. They were the so called ‘paris group’, that had studied abroad on scholarships. This was at the time an exceedingly rare occurrence as the vast majority of Khmers didn’t have adequate access to education let alone university level qualifications. The way they got there is due to their higher than average financial situations that gave them an avenue to study in Phnom Penh and then abroad. This does not strictly mean that they were part of the Chinese urban class which dominated some sections of the Cambodian economy. It doesn’t really make sense to project their sino-khmer heritage onto an idea of the CPK being dominated by a Chinese class. They were Khmer through and through.

Rather than viewing the leaderships’ ethnic background and questioning the treatment of Chinese it may make more sense to question this treatment in regards to the fact that the Chinese were far and away the Khmer Rouge’s biggest benefactor and ally. It always struck me as odd that a high percentage of Chinese died when this was the case. But then, when you consider the millions and millions of Chinese that died as a result of Mao’s policies… maybe it didn’t matter too much to Beijing.

Key to understanding communist revolutions and the death tolls associated with these movements are the ideas of progress which underpin such radical efforts to transform entire countries. In China, or the Soviet Union, if millions of people starve to death in the process of becoming a fully realised communist nation then that is just the way it was going to be. This is where the is a divergence in the literature between the historians who consider the Khmer Rouge ideology to be primarily motivated by goals of totalitarianism, expansionist and racially motivated ideas or more concerned with Marxist-Leninist doctrine.

If you follow Ben Kiernan’s approach you will likely decide that decisions by the CPK to ban Chinese language and to kill Chinese people indiscriminately in the later stages of the regime were motivated by genocidal ambitions – which would as you suggest be a strange thing considering the Sino-Khmer ancestry of some of the leadership.

If you are more inclined toward Steve Heder’s analysis of the CPK you will place these, and other persecutions against minorities in DK (such as the Muslim Cham) as being motivated by ideas of ‘class struggle’, rather than racialist theories. As such the death rate of the Chinese is explained by the disproportionate suffering during the regime of the classes of people who were ‘bourgeoisie’ or ‘capitalist’ in the pre-revolutionary period. Bans on Chinese language is not seen as specifically targeting the Chinese race, but rather as the goal of assimilating the entire nation into one new group – Kampuchean. The more distant you or your ethnic group or economic class fell from this ideal new Cambodian would correlate with the amount of suffering you would likely incur during DK or the likelihood that a misdeed would be punished by death. This does not mean that treatment of the Chinese was not racist – but that this racism was based on class categories first and foremost rather than some kind of racial hierarchy that would be familiar to say – the Nazis.

Cadre in the zones/commune level were often given large categories that defined the enemies to the regime or signs of ‘regressive traits’ or, lack of ‘proletarian consciousness’, which would mean people displaying characteristics that fell into these categories were more likely to be killed or treated worse. For an individual cadre it would be possible to assume that they might simply kill a Chinese person, or family because it would be assumed that they were ‘useless’ and they did not fit into Pol Pot’s Marxist vision of socialist modernity. There were numerous instances of persecution – and widespread killing – of the Chinese, rural and urban, based on ethnic grounds and generalisations of the Chinese race as a class.