1) The entire discussion is a rehashing of the exact same points every time the topic is posted, and not very insightful
2) The participation rate for experts (or even authors) in the discussed field/topic is very low (compared to programming topics)
3) The discussion rarely stays civil and requires excessive moderation
An observation (have no verbatim quote, but believe from dang) is that there is a significant base of "anti-political", otherwise "known-good" HN participants, that flag topics like this preemptively pretty much regardless of perspective and exact topic (presumably for above reasons). You can certainly still blame the flagging on bots or Zionists, but it's almost certainly not only those.