Labeling it a "theory" is simply the correct approach. As with the General and Special Theories of Relativity posited by Einstein, the Big Bang theory has not yet been fully tested and explored, and has not, as yet, achieved the status of a scientific "Law."

Yes, I am well aware that all 3 of the theories mentioned have yet to be disproved by any evidence and have survived a number of specific efforts to test them, and that the Theory of Intelligent Design borders on the tautalogical as it does not admit of testing in the fashion prescribed by the scientific method.

Therefore, the chap at NASA was correct, albeit probably a bit too picky. As to whether he was motivated more by an outside agenda than by a penchant for detail, I cannot say.