Even a 50 page book is too long (although perhaps a good next step) because I can't get this person to read non-fiction (yet).
I need something *short* to cool them down from thinking the entire world is just waiting for us to let our guard down, to kill us all. (Anything that strongly re-assures that libertarianism is not pacifism and that self-defense is still on the table would be helpful.) Some kind of short essay or online article...
Also helpful (they read lots of sci-fi/fiction) would be any futuristic novels that chip away at this mindset, if any such books exist. Something that strongly parallels the 'war on terror' thing would be ideal.
Science fiction is pretty much a gold mine for finding books with libertarian themes.
http://io9.com/5254742/10-greatest-libertarian-science-fiction-stories
Robert A Heinlein is great, although some of his themes are conflicting.
Also you can't go wrong with 1984, the war propaganda bits seem especially relevant to your friend.
Try this: http://www.youtube.com/watch?v=muHg86Mys7I
Clayton -