Apparently, the AF Academy Prep School cadet did it thinking he'd somehow duck his impending expulsion or set back or whatever it is he was being rung up for prior to scrawling those words. If he's that stupid then he shouldn't even be allowed to come close to a military officer's commission. I can imagine the trouble he'd have gotten himself into down the road, when he had responsibility for leading and directing subordinates.
You're right: a TON of these incidents turn out to be hoaxes. Much the same thing turned out to be a hoax around these parts just a couple weeks ago, over at Eastern Michigan University. Same social justice warrior scenario: Black person writes racist graffiti, school goes into full-on meltdown mode, lectures everyone else about the need to check their privilege -- whatever the hell that is -- and orders sensitivity training for perceived transgressor races (i.e. white folks ;-) and offers so-called "safe space" for the transgressed.
College administrators and educators these days have almost no backbone when it comes to these things. Typically, due process and a calm, complete and competent investigation goes right out the window, too.
"Politics is just show business for ugly people."