I think that the question was partly philosophical -- how certain can we be in the things we believe we know is one of the classic epistemological questions. It is also inherently mathematical, and certainly the fact that I am a working research mathematician first and some guy who took a couple of philosophy classes in college second informs my response. [I will say that the question is not phrased in a way which evinces much mathematical or philosophical sophistication: it comes off as somewhat naive. Perhaps this was part of what made it problematic to those who voted to close.]
I am a bit surprised that everyone seems to agree that philosophical questions are a bad thing on a Q&A site about math, and that the term is being equated with the sufficient conditions for closure "subjective and argumentative".
I well understand that most contemporary research mathematicians have little to no knowledge of or interest in philosophical questions (or if they do, they keep it to themselves in roughly the same way that many people try to keep their religious beliefs out of "secular" conversations). For a site like MO, which is focused on the specific needs of research mathematicians, it is reasonable -- or at least, not a big target for surprise or outrage -- that questions with philosophical content are not especially valued. Frankly, at the moment MO has little content concerning the connections between mathematics and any adjacent fields -- even when theoretical physicists appear to talk math, the (understandable) cultural differences between math as done by mathematicians and math as done by physicists often intervene to make the physicists' contributions less than well received. Similarly I have seen almost no questions on the border of math and engineering, math and biology, math and economics, etc. (although there has been some sentiment on the meta site that MO should be, somehow, much more encouraging of such questions; no one has campaigned for math and philosophy that I can recall).
But the point of this site, as I understand it, is that it is supposed to have a broader appeal, and explicitly to cater to connections between mathematics and other fields. Are people really saying that there is no room here for mathematics and philosophy? I would find that to be rather disappointing.
Added: Sorry, once again I completed my reading of the links in the question only after crafting an answer. In the meta.MO thread that Kevin links to, [Andrew] Critch takes a position which is pretty similar to mine here: i.e., philosophy is not necessarily equal to discussiony and can be compatible with mathematics. But that was in October 2009 which is a loooong time ago in the history of MO.