We don't really need to discuss it further, but, to clarify, I think the thing that caught my eye is when a reasonable discussion naturally starts to veer towards these more difficult, ideological topics.
Those topics aren't meaningless. It is just very hard to discuss them productively on a public internet forum, as you noted. However, it is also not unexpected for productive, intellectual discussions of other issues to meaningfully brush up against these "ideological tangents" on occasion.
The part that seems a little arbitrary to me is to say that the discussion can't proceed further purely based on content alone, as opposed to instead drawing the line based on content-neutral criteria such as civility, substantiveness, novelty, etc.
But I understand that this desire may be overly idealistic in a public internet forum, and certain pragmatic lines may need to be drawn. It sounds like might be the case on HN. Again, thanks for engaging with me on this.
Such discussions are off topic for a reason: they are repetitive. Worse, they turn into flamewars (case in point, see the replies to my comment downthread). This is emphatically not what HN is for. The value of this site—intellectual curiosity—withers under repetition and dies under attack.
Take a look at the comments through the search link I posted. There's a long history there. If you then still don't understand why we're doing this, I'd be happy to discuss it further (but you'll probably need to email [email protected]).