I hate the TSA as much as anyone, but this type of gallows humor is pretty common - in private, it's common for doctors to joke about dying patients, etc, because keeping things deathly serious all the time is emotionally impossible.
But as you said yourself, there are situations in which this 'humor' is appropriate. The official blog of a government agency is definitely not the place. I would expect this type of language from a no-name blog by a person with the grammar of 16 year-old.
