One reason could be that it quickly devolves into Jew hatred, as the replies to your comment already has. I rarely see stories about the US getting any comments on how Americans make bread out of babies. I would much rather not have that on HN. This is not 4chan.
You're referring to https://news.ycombinator.com/item?id=41066729. That comment was rightly flagkilled by users, but I believe you misread it. It was sarcastic and meant the opposite of what it appeared to be saying. In other words, it was more or less agreeing with your own view.
HN does get some genuinely antisemitic comments, most of which get posted by one or two serial trolls who keep making new accounts. We ban those whenever we see their latest incarnations—it's a whack-a-mole thing.
You're right this is HN not 4chan, because none of the things you said have actually happened here and people can easily have good respectful debate. It feels like you're attempting to use this as a way to silence debate around the country of origin rather than anything else
It did happen: https://archive.ph/KT4q8 and to be quite frank, that is just the most egregious example and this thread is anything but respectful debate with statements like "I've taken to using it because i feel uncomfortable even naming them a lot of the time" and implying that HN is somehow afflicted by institutional corruption.
All: if you turn 'showdead' on, please don't forget that you did so, because we sometimes get emails from people asking "how can you possibly condone $horrible-comment appearing on HN?" when in reality the account has been banned for years.
EDIT: I have receipts, https://archive.ph/KT4q8