TL;DR Summary

• This propagandist is using the humorous observation that  many propaganda posters are not true – and twists that to its advantage.
• Since it is funny, it will be shared more widely.
• Politifact did rate it true, albeit, after a lengthy explanation. More from the Committee for a Responsible Federal Budget.

Humor can be an effective method of engaging the target, emotionally. Further, funny items are likely to be shared with others.
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Obama says he has cut the national deficit in half. Politifact finds that statement TRUE!!