For a beautiful worked example of this technique, see this classic Twilight Zone episode:
http://en.wikipedia.org/wiki/The_Monsters_Are_Due_on_Maple_Street
Ending narration: "The tools of conquest do not necessarily come with bombs and explosions and fallout. There are weapons that are simply thoughts, attitudes, prejudices - to be found only in the minds of men. For the record, prejudices can kill...and suspicion can destroy...and a thoughtless frightened search for a scapegoat has a fallout all of its own - for the children...and the children yet unborn. And the pity of it is...that these things cannot be confined...to the Twilight Zone."