I'm not so sure this guy has got it right - I remember watching the movie 'Signs' right after the war started, and at first I was afraid it was going to be one of those movies about how horrible it is to give in to our "irrational fears", cause there really weren't any aliens or anything to fear, and if there WERE aliens, we should sit down and have a nice long talk with them. But as it turned out, the message was that our fears are justified, and instead of talking we need to smash their heads in with a baseball bat.
That is the best plot summary of Signs I've ever read.