[dionidium]

"SO would suffer, because the kind of question you're talking about is intrinsically debatable."

That's certainly a claim and it's a claim that the SO folks also make, but I still haven't seen a single piece of evidence that it's true.

[fusiongyro]

If it isn't obvious to you I doubt anybody will be able to "prove" it to your satisfaction. Besides, you can't create rules around impossible conditions like "close any question which will lead to endless debate" so instead you create rules around easily detected conditions like "close any question that isn't concrete."

I don't greatly love SO (though I like it more than I used to) but there are lots of alternatives that lack SO's irksome limitations (slant.co comes to mind). By now it is obvious that whether you like SO's formula or not, it clearly works.