The fact is, of course, that "terrorist" doesn't actually mean any such thing. Hence, there's an almost unconscious cognitive slide being encouraged by this misuse of "terrorist": one starts by thinking of someone who is evidently a bad guy (kills innocent people in order to spread fear and thus achieve political goals) and ends up thinking of anyone who is an enemy. Hence, one is encouraged to combine the aspects of the two concepts: one is encouraged to think of any enemy as someone who wants to kill innocents and spread fear. (This is why Howard Dean gets compared to a psychopath (Google search.) It is, in fact, pretty infantile as persuasive tactics go: as long as one keeps straight what ideas are actually in play, rather than what words are being used, one cannot be tricked by this sort of maneuver.
What's worrisome, but not surprising, is the corporate media's complicity in the blurring of the two concepts. What's even more worrisome, and rather surprising, is the ease with which many Americans have accepted the redefinition.