Well it’s true many Cambodians tend to be hateful towards Vietnamese. The Vietnamese have liberated Cambodia from the Khmer Rouge, but apparently the Cambodians don't like Vietnamese even today. To begin, there is historical animosity. The southern third of Vietnam today once was part of the Khmer Empire. Vietnam and Cambodia fought at different times, and less than two hundred years ago Vietnam had invaded Cambodia and installed a new monarch. So there is a revanchist quality to this. Cambodia still claims parts of the border area between Vietnam and Cambodia, and there remains a large ethnic 'Khmer Krom' population living in what today is Vietnam's Mekong Delta.

Under the French colonial Indochinese federation, Vietnamese were by far the numerically superior group. And because most of the modern training institutions were based in Vietnam, they also dominated the colonial bureaucracy and community in Phnom Penh. French colonialists believed the Vietnamese were the more robust race, superior to the Khmer and Lao. This gave rise to a saying that went more or less: 'a Vietnamese will plant rice, the Khmer will sit down and watch him plant, and the Lao will lay down and listen to him plant'. When Cambodia emerged from independence, many saw it as the end of two colonialisms, one French and the other Vietnamese.

Regarding the Khmer Rouge period, keep in mind that the Ho Chi Minh trail ended in Cambodia’s sovereign territory. As the war escalated, these foreign Vietnamese troops further pushed into the Cambodian countryside away from the Cambodian-Viet border. With them came more bombings, more fighting, and a foreign authority. Though they toppled the Khmer Rouge, the subsequent occupation was another period of Vietnamese occupation from their perspective. Hanoi did not plan it as an humanitarian mission. The aim was removing a defiant Pol Pot who had invaded Vietnamese territory and refused to work with the Vietnamese SRV government. The Vietnamese would occupy Cambodia for the next decade.

Beyond that Vietnamese can often have a patronizing view of the Khmer and Lao (just as some Khmer have a very dim view of Vietnamese). It’s not uncommon to hear some Vietnamese talk idyllically about a new Indochina federation. For them the idea sounds wise and natural. Their vision is of a bigger political space, once again guided by Vietnam. For Khmer, this sounds like the return to yet another era of Vietnamese political domination.