That's the very point. What we are discussing is not why a particular post was down but whether the policy of completely shutting the discussion makes any sense

That's the very point. What we are discussing is not why a particular post was down but whether the policy of completely shutting the discussion makes any sense. You could argue that if a discussion is heated, at some points both sides run out of arguments and things like Godwin's law kicks in, so letting it continue is counterproductive. On the other hand, I saw interesting and highly upvoted posts disappear after just a couple of comments (because they were politically incorrect, criticized someone, or were in favor of someone currently out of fashion). This "I dislike so I flag" abuse (by a minority) is my single gripe with HN. Otherwise, it's by far the best community on the web and I'm happy to be a part of it.