The point Neally is trying to make (and you are completely incapable of comprehending, apparently) is that there could be any number of outside factors that make your conclusions "I saw you at the mall yesterday" wrong. How far away were you? Did you see their face full on, or only from the side? Did you see a face at all? Did you call out the name of the person you thought it was and receive an acknowledgment? Can the person whom you claim you saw prove that they were, in fact, elsewhere at the time you thought you saw them? These are all factors that affect the statement "I saw you at the mall yesterday".
Likewise, when we look at the video provided, we can hear what is being said, but without independent verification through corroboration (which we do not have), scientific analysis of the substance in question, (which we also do not have), or further statements from Mr. Riggs where he states unequivocally "I saw melted steel while helping to clean up Ground Zero" (WHICH WE DO NOT HAVE), then we cannot say definitively that Mr. Riggs in fact saw molten steel (in its liquid state, that is). The fact that you don't get that makes me wonder just how disconnected with reality you are, quite honestly.