Actually, if you look up theory in the dictionary you will find definitions for both the lay use and the scientific use. When discussing a scientific topic it is logical to use the scientific definition.
Unless, of course, the other definition would make a good weapon for your side, in which case a little deliberate misconstruing is forgivable since it is more important to win than to be truthful, right?
Otherwise known as the "Fallacy of Equivocation".....