Consider what Harper accomplished with his propaganda. He convinced 162,000 former boat people and their descendants, perhaps as many as 400,000 people in total, that they needed to either identify as nationals of the Saigon regime or disappear from public view.
He convinced all Canadians not to object to a pro-Saigon policy that formally recognized a defunct military dictatorship as a legitimate government and a military ally of Canada.
He convinced Canadian politicians of all parties to enthusiastically demonstrate their support for his policy.
The answer is, he did it with an alternate reality and some dog whistles.
The boat people
This group presented a number of problems for Harper:
They were a diverse group that came from all over Vietnam between 1979 and 1996, thus in conflict with Harper's story that the origins of the community lies in the fall of Saigon and the Saigon military.
Most likely to be upset by Harper's reframing of the Vietnam war and would tell the conflicting stories about what had caused the Saigon regime to collapse.
They knew the true meaning of the symbolism that Harper was using to hide his pro-Saigon policy and were likely to reveal that to the media.
Luckily for Harper, this group was as vaguely attuned to what Canada's reaction had been to the fall of Saigon as were other Canadians. And as with other Canadians, they were familiar with the story of how the US and responded. Harper successfully convinced them that his revised history of the boat people crisis was true. He put them into an alternate reality were they were no longer refugees in Canada's eyes, while the former Saigon military were legitimate refugees.
Even in normal circumstances many would have been ambivalent about speaking out against Harper's pro-Saigon policy, but this alternate reality made it impossible for them to do so.
Harper enhanced the discomfort of the former boat people with a little hostility and intimidation.
All of those symbols that we described above as dog whistles have another meaning to Canadians of Vietnamese origin.
They read them as direction that they must identify as nationals of the Saigon regime or else there status as Canadians will fall into doubt. Vietnamese understand the symbolism of the Saigon regime because it has existed since 1955 and it has the same meaning today as it had then: identify as a loyal national of the regime or disappear. It gained new strength coming directly from the government of Canada.
Just in case the younger generations did not "get it", Jason Kenney had made the message quite explicit in 2008, and that message has been repeated often by Harper's supporters.
There is a striking demonstration of how successful Harper's deception of the former boat people has been.
Occasionally a former boat person, or family of one, has been determined enough and articulate enough to speak to politicians about the government's hostility toward Canadians of Vietnamese origin. They never succeed because the adopt they posture that Harper's myth has created for them: that of a minority speaking out against the government's pandering a distinct cohort of former refugees to whom Canada has a moral obligation. No politician will touch their complaint when it is framed that way. Harper knew what he was doing.
No one will get the attention of a politician until they firstly self-identify as a legitimate refugee or family and secondly describe Harper's favoured group as a "political faction". Government can legitimately and effectively be criticized for adopting a small political faction as representative of all Vietnamese -- failing to acknowledge the diversity of Canada's Vietnamese community.
In addition, the government is not pandering to any Vietnamese group. The government is using the Vietnamese to change Canada's national identity to a nation of communist-fighters. There is no part of Harper's program that is not offensive to all Vietnamese.