I listened to his arguments, I presented arguments why Chinese people feel like Vietnam should at least be an ally.
This thread is literally called China's SCS strategy thread. Yes a divided China is in the long term interest of every country around it, that's why literally everywhere online is talking about intervening in China's reunification. You don't think Vietnamese defence forums discuss how to deal with China?
You can close your eyes to unfriendly ideas, but you can't deny that many of China's state funded assistance projects to Vietnam have been in the North. New railway connections to China and not North to South high speed rail. Subway for Hanoi and not Ho Chi Minh city. China has been trying to weaken Vietnam's grip on Cambodia and Laos for decades, rail and canal infrastructure is just part of the process. Just because the Chinese government doesn't overtly promote anti-Vietnamese topics, doesn't mean they don't exist.
China dividing strong countries on its doorsteps is not a new thing, it's been going on for millennia.