There are some that argue the monarchy constitutes a human rights abuse both against the people she took tax money from and against her own family which was forced to participate in the pageantry.
Calling those opinions "flamewar tangents" is incredibly dismissive.
The GP comment was definitely a flamewar tangent: 'flamewar' because it's a classic political battle, and 'tangent' because it touches the original topic at one point and then veers away from it.
Tangents can be fine if they're unpredictable, but generic tangents are predictable and those are the worst sort of thread on HN. They're so predictable that they're the opposite of the curious conversation we want here.
The number of comments criticizing moderation in this thread is not because I used the word flamebait. I've used that word thousands of times on HN. Rather, it's a function of my screwing up with https://news.ycombinator.com/item?id=32769925. That happens sometimes—usually when I mis-pre-assess people's feelings.
As for it being "flamebait", within this context anything that motivates this classical political battle will be a comment on the opposite side of a topic to one's own opinion. Moderation would need to be balanced in restricting such comments to effectively restrict "flamebait" - yet only comments on one side are being killed.
Edit: Further, some topics, no matter how carefully broached, are just a bad value proposition. They may have a bad ratio between their intrinsic value (importance, relevance, etc) and how likely they are to spawn a low-quality thread (and how low that quality is likely to be).
Edit to match yours: If this convo is so fraught, Dang should delete the whole thread.