You can use HN Search to verify that HN sees plenty of comments "saying anything against China". The topic is extremely flame-prone because people are wont to hurl generalizations at each other, and worse. Nationalistic flamebait and flamewar is a big problem on HN [2] and destructive of the spirit of this site [1]. Individuals have been attacked here for just for expressing their views while being (or being assumed to be) Chinese, and at least one person was hounded off the site altogether. I'm sure you'll agree that that's shocking and not at all the community we want to be. None of us wants it, but it's easy to get it anyway, once such flames get going.
I don't think your comment was nationalistic flamebait, except insofar as it was rather unsubstantive. Unsubstantive comments on inflammatory topics are guaranteed to come across in a flamey way to some segment of the readership, even when that wasn't your intent. Intent doesn't communicate itself, unfortunately, so the burden is on the commenter to disambiguate [4].
[1] https://news.ycombinator.com/newsguidelines.html
[2] https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...
[3] https://news.ycombinator.com/item?id=21200971
https://news.ycombinator.com/item?id=21195898
https://news.ycombinator.com/item?id=19404162
https://news.ycombinator.com/item?id=22608635
[4] https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...