Yes, the US military really did produce a cartoon instructional manual about Don't Ask, Don't Tell. And the American government is by no means the only entity to use cartoons in humorless way.
Indeed, if you're going to shove your political agenda down people's throats, there may be no more entertaining method than comics. Which is precisely why Comic Art Propaganda: A Graphic History is so inviting and unnerving. In this collection of cartoon agitprop, Fredrik Strömberg, a Swedish comics expert, surveys everything from evangelical Archie strips and hysterical Cold War fantasies to '70s feminist comics and 9/11 kitsch. Much of the material is laughable, but artifacts like legendary cartoonist Milt Caniff's wartime pamphlet "How to Spot a Jap" remain vivid illustrations of comics' inflammatory potential.