China kept backing Khmer Rouge despite the millions dead and even invaded Vietnam to protect them. Amoral, self interested actor at best. There's nothing North Korea could do to their own people to change the support.
The realpolitic of international relations very often follows the words of the British prime minister, Lord Palmerston: "We have no eternal allies, and we have no perpetual enemies. Our interests are eternal and perpetual, and those interests it is our duty to follow."
This claim doesn't appear to be true: https://www.reddit.com/r/AskHistorians/comments/1k6yi1z/comm...
And by the time you managed it the falsehood already netted a few dozens/hundreds/thousands more victims in the best case scenario where the rebuttal actually managed to attach itself right next to the falsehood.
Regular folks just can't compete with professional disinformation spreaders and their horde of victims.