A couple reasons. First, it's a matter of degree. Arguably https://news.ycombinator.com/item?id=29659145 was a step in the wrong direction (the generic-nationalistic direction) but https://news.ycombinator.com/item?id=29659160 was clearly much worse.

Second, I wasn't responding to just the one comment but to an obvious (and very bad) pattern in the comments by that account. Note "you've been doing it a lot, unfortunately". The reason we'd ban an account is because they posted one comment like the GP, but because they're making a habit of breaking the site guidelines.

I hope it goes without saying that these moderation calls involve no relative assessment of threats to national sovereignty.