Most are recent, very recent in fact, and it is the direct result of propaganda from Le Duan (1976-1986) time. In the past, more then 100 years ago, the relationship actually are good and the cultural tie is deep.They hate China for the Sino-Vietnam War of 1979-90 or this hatred roots back a millenia?
The tension between Vietnam and China raised as a direct result of the Soviet - China tension and the decision of China to align with the US in the 70s. In the end, Vietnam chose the Soviet and signed a alliance treaty with the Soviet. Right after that, the propaganda system of Vietnam, learned from the Soviet has worked full time to demonized China and Chinese.
The policy to align with the Soviet cost us dearly
The rest is history, the Soviet lost, Vietnam lost the whole war (1979 - 1989), Vietnam has to come to China for peace, Cambodia fall back in China camp, the islands lost.
Now with the US-China tension, the US actively push the propaganda against China as well, hence the result: they re-use some propaganda of old and push that to social media
However, since 2019 - 2020, the US lost heavily in virtually all front, the propaganda in social media become more and more ridiculous.