They don't care they just need enough nationalist supporters to drowned out the majority.
Stop giving credit where none is due. The Vietnamese government isn't the problem, the Vietnamese people are. The CPV is a calming influence on the wider population just as the Saudi royal family is a calming influence on the fanatical Saudi population.
There's this weird tendency in the West to separate people from government as if the latter is always exploiting the former and the former is never at fault. Sometimes, in fact, most times, the people are just as bad if not worse than their government. The government, after all, are composed of individuals who, before they became officials, were part of the wider population, and they reflect the wider views of that population.
Just as the wider Chinese population holds Japanese in disdain for their disgusting conduct in WW2 and their cowardly refusal to own up to them, the CPC simply reflects this disdain in their PR releases and education program. This isn't a matter of the "evil Chinese government misleading the Chinese people", it's exactly the Chinese people themselves who demand the government address the Japanese issue the way they do. Likewise with Vietnam, it isn't a case of "Vietnamese government misleading the people", it's the Vietnamese people themselves who have a fanatical and irrational hatred of Chinese despite China having never marched an army down there to massacre their civilians.
There is no need to propose the existence of a complex theory of conspiracies and motives of an abstract Vietnamese "elite" or "leadership" to mislead the population into hating China, and indeed Occam's razor tells us not to. The simple truth is the Vietnamese people at large hate China without any input from their government.
And frankly, it's attitudes similar to yours that got them into hating China in the first place. You seem to think their population doesn't have the capacity to decide for themselves who to hate, as though their government is an omnipresent and omnipotent beast that brainwashes them into specifically hating China. That's extremely condescending way to think of Vietnamese and is essentially what the West thinks of China; as though Chinese people are retarded drones who can't decide for themselves what opinions to hold without input from the CPC.
This condescending attitude is what lost China most of her "allies", or more accurately, tributaries, and made them defect to the first available outside power. It's prudent to accept the reality that the Vietnamese PEOPLE, not their government, passionately hates China in their very bones. They have the capacity to feel this hate without their government's telling them so. Once you accept this reality, whatever solutions you come up with to deal with the Vietnamese will be far more effective and enduring. Right now, you seem to propose something akin to a regime change to install leaders who will not spread anti-Chinese propaganda. Yeah, that is
never going to work. The Vietnamese people will not tolerate a government that doesn't reflect their views, and their view is China needs to be hated with all their heart. But because you think the problem lies only with their government, you think changing the government is going to solve the problem. It's not. The Vietnamese will overthrow the installed government and establish their own, except this time, they'll hate China even more (if that's even possible) for attempting to interfere with their country's internal affairs.
I have no viable solutions to the Vietnamese issue but I recognise it's not their government that's the root of the problem, it's the entire goddamn population. Whatever solution is adopted to address the Vietnamese problem MUST be applicable to the population, not just their government. To this end, please stop separating the CPV from the V as that will only fool you into adopting "solutions" that will not work and will just end up making the problem even worse.