I am not sure if the writer is a Vietnamese or a Khmer with Vietnamese head (kbal yuon, kluon Khmer), but he got history very wrong. He said Khmer Rouge attacked Vietnam unprovoked. The fact of the matter was that Viet soldiers encroached on Khmer border everyday like they are doing now and the KR soldiers tried to stop them, that's why the Viet launched a full scale war and invaded Cambodia.
The writer also said that Vietnam's invasion was "the most profound and true humanitarian act". The writer forgot that Vietnam was the one who created the KR, helped KR came to power in 1975 and then aided and abetted the KR in the killing of millions of Khmer life through Viet tricks. Vietnam did not come to save Khmer life, but invaded to annex more Khmer lands and kill more Khmer life like the K5 Plan. In fact, there are many claims and statistics pointing out that many more Khmers died or were killed after the Viet invasion in 1979.
The writer also accused overseas Khmers for inventing the story of Viet encroachments. No one will believe this claim because people can see with their own eyes that Vietnam are encroaching Khmer territory everyday and that Khmer farmers living along the border are crying everyday because Vietnamese soldiers had encroached on their lands. Does this writer think that these poor and unarmed Khmer farmers are the invaders of Vietnamese territory?
Regarding Champa and Kampuchea Krom, well, it is history but don't claim that they were Viet territory and the Chams and the Khmer Krom were invaders, right?
I believe that Cambodia and Vietnam should be friends, but do you think that friends won't invade or encroach on each other's land, right? I believe that we Khmers can't take back Kampuchea Krom, but we must never allow Vietnam to continue to encroach or chip away our territory on a daily basis. If you think that I have made up the story of Viet encroachments, then you just ask the farmers living along the border and they can tell you that they lost their land everyday.
History should be told the way it had happened, not twisted and turned.