And when Vietnam invaded Cambodia and stopped the genocide in two weeks, this happened:

> Although Sihanouk distanced himself from the human rights abuses of the Khmer Rouge, he accused Vietnam of using aggression to violate Kampuchea's sovereignty. As such, he demanded all UN countries suspend aid to Vietnam and not recognize the Vietnamese-installed regime. Subsequently, seven non-aligned members of the UN Security Council submitted a draft resolution calling for a ceasefire and the withdrawal of all foreign forces from Kampuchea, which was endorsed by China, France, Norway, Portugal, the United States and the United Kingdom. However, the resolution was not approved due to opposition from the Soviet Union and Czechoslovakia.

https://en.m.wikipedia.org/wiki/Cambodian%E2%80%93Vietnamese...

Your article says “allegations”, but you’re stating it as fact.

Your link says "Allegations". What is proven? Not much. The article suggests the U.S. was not too keen on Vietnamese occupation of Cambodia and when they did actively support a group it was the non communist groups. China and Thailand actively supported the Khmer Rouge.