Please, if the question needs to be (down voted and) closed, can you find a valid reason for closure as this is not a duplicate question? One asks for the mass launched into Space. My question asks how much mass was required to make those launchs possible. Granted, it may not be the best question ever posted, but it is a valid question none the less. Close it if you must, but if you do, please revise the reason why it needs to be closed.
Writing a meta question on this is a good call. If you have a problem with anything on the site, meta is the place to start. When moderators are appointed, they ought to be reading every new meta question (they will be notified of them, at least). A meta question also allows the community to weigh in on the issue.
About the question. It does sound like a duplicate. I realize it isn't since you are asking about the total mass of the propellant used and not the mass put in orbit. But the question is a bit unclear on that point. So I hope you can see why folks might think it's a duplicate.
Now, I see you tried to clarify that aspect of the question with some edits and that there was an edit or two to correct a perceived criticism of space exploration itself. That's a good approach in general—fix closed questions when you can.
However, none of this addresses the fundamental issue with the question: it doesn't make sense from the perspective of the sort of experts this site is hoping to attract. The first comment captures the issue well:
Are you asking about our permanently "exported" mass, also about temporarily exported one (satellites in decaying orbits, returning probes, shuttles, e.t.c.), or just the total mass of any spacefaring vehicles, if they returned or not, burnt large portion of their mass in our atmosphere, or not, i.e. - how much does mankind's space exploration weight, throughout its history, if you'd be able to put it on a scale?—TildalWave
If you look at the other comments from TidalWave, you'll him saying more or less the same thing several different ways. Almost all the propellant we use to launch stuff into space will fall back to earth at some point or another. So the question is underspecified.
Now about the closure: we could reopen and reclose with some other reason (my vote would be "Unclear what you are asking"). But it would be better if you addressed the problem Tidal elevated.
I personally voted to close with the "unclear what you're asking" reason, but I guess others thought otherwise later, after your question was edited to read, in my opinion, substantially differently than what I thought (but wasn't sure) you wanted to ask initially. I tried working with you in the comments to further specify precisely what information you were asking of us, and possibly how you figure we should go about calculating it, but we obviously didn't manage to understand each other, before it was edited.
I thought the question was worded vaguely, and could be interpreted in too many different ways, so I voted to close with the reason mentioned before, possibly an hour or more after I first read the question. My reason was, that since your question was ambiguous and could be interpreted in many different ways, potential answerers could sacrifice a great deal of time and effort in trying to answer it, only to fail due to imprecise definitions. I believe that's a reason enough to vote to close a question, at least eventually, after failing to convince you that the question needs to be edited by you, but feel free to correct me in the comments below.
Essentially, your question (the original one, written by you) didn't specify in units of what you expect answers to present information. As we measure anything non-subjective in precise units of measure (even if the figures are ballpark, at least we know they're in some range of something measurable), which is how answers on websites about precise sciences and technology should IMO be, I thought I was asking valid questions in my comments to your question.
I think the question could easily be salvaged. The votes can be reversed or removed by those that would feel the new edit warrants it, and the question can be reopened, if it meets criteria of five of our reviewers (members with enough reputation) - just so we understand each other - criteria for questions isn't anything personal, we're all (and you're welcome to join this process as well) working hard to define it. But I would, again, ask of you to be precise and specify what you mean. I realize that it's sometimes hard to write questions that would be read in the same manner as when you are thinking of them, and in my opinion some essential information was missing from yours for us to form same thoughts and understand each other. It happens. But that's why we have the comments section, where we can work together in making your question answerable. And the way it was first written, I just don't believe that it was. I wanted to research the topic and post an answer, but I didn't have a clue, if I'll be spot on, or miss by a mile.
So, TL;DR - No biggie, rewrite your question and follow suggestions in the comments to make it better and actually answerable, and I'll be glad to vote to reopen it. If enough of other reviewers will agree, it will be reopened, and can later be - hopefully - answered, too.
This should be fixed, not ignored. Keeping it closed as a duplicate does more harm than good. There is benefit to keeping duplicates around, while questions that are out of scope should eventually be deleted.
If you don't have any intention to try and re-write the question to bring it into the scope then it should be closed under a different reason than "duplicate". However, I would encourage you to try and improve the question so that it is within the site's scope.
In the absence of mods, I have flagged the post so that a SE team member can hopefully amend this.