Don't bother much, that user just replies with "but the relative impact is low" to some of the most well-supported and obvious examples in this thread that argue presence of significant historical influence of imperial China on the region. In your case it was about confucianism, in one other, it was about kanji[0].
I also studied Asian history as well, but I studied it in Asia. I often come across a lot of Americans who study Asian history from a Sinocentric viewpoint which is why I write strongly on the matter.
0. https://news.ycombinator.com/item?id=36118362