If you're going to comment in this thread, please make sure you're up on the site guidlelines (https://news.ycombinator.com/newsguidelines.html) and note this one: "Comments should get more thoughtful and substantive, not less, as a topic gets more divisive." We don't want political or nationalistic flamewar here, and any substantive point can be made without it.
You repeat, above, that HN is not for nationalist flamewar, and requires substance. But this post is nationalist flamewar and isn't substantive. Allowing it while shutting down similar content from the opposite perspective is... unsettling.
Edit: Ok, I've read the first half and looked over the second half, and I think the moderation call was the correct one. Not saying this to pile on; I just wanted to report back.
But also just look at what happened here in the comments. It's totally predictable. Those of us that read the article and flagged the post had prevented this. In this case flagging had worked and was not abused.
I don't think the comments were as disastrous as you suggest. It's true that the majority were negative, but not all—and in any case, it's important that HN's front page not just be a product of majoritarian sentiment. If it were, then we would clearly be failing the core principle of HN (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...).
Did I pick the right hill to die on at the hands of the majority? Maybe not, but (a) the sentiments would be the same if I had; and (b) we have to take some chances; if we don't, we fail for sure.