Memes

There was a tendency in this era to adopt extremist positions in reaction to the USSR and Kruschev and the fear of something similar happening in China. Even in China itself, this led to the excesses of the Cultural Revolution, with student-led militias killing each other, committing atrocities, performing show trials, etc. There was overcompensation that, afaik, went beyond anything that happened during the actual revolution, and some of it was just maximalist rhetoric thrown around to performatively demonstrate how unlike the revisionist Soviets they were, sometimes without really meaning it.

The Khmer Rouge was kinda like a kid getting relationship advice from someone going through a messy breakup. They took the most extreme rhetoric going around in China and internalized it. The Chinese communists didn't really educate the Cambodian movement on basic tenets like "don't be racist," that the fledgling Cambodian movement actually needed but which the Chinese likely took for granted, and instead just emphasized, "don't be revisionist." For the same reason, the PRC wasn't really watching out for the possibility of them becoming too violent/genocidal.