The key problem I have with your #2 is that it ignores what people actually mean when they say "can't". When I say I can't lift that rock over there, I don't mean that if I went and trained for a few years I wouldn't be able to do it: I mean that if I went over there right now and tried to lift it I would fail. When you realize that this is what normal people mean by "can't", suddenly concepts like "XML can do something JSON can't" make perfect sense: there exists a tool/library that makes that happen right now, and for JSON it is some theory that you have that would require sitting down and spending a bunch of time coding. (And no: those people don't "actually believe" that JSON could never be made to do those things ever: the more you interrogate them on this matter the more it will seem that way as they are going to keep saying "can't" and it is going to keep meaning something different from the way you are using it.)