A concerned driver called 911 to report the "totally disgusting" image, and the FBI kicked off an immediate investigation, because apparently the FBI's time is much less valuable than we previously assumed. It turns out all it takes to hack into one of these eye-broiling behemoths is to track down its web interface, type in a password that the sign's owner probably never changed from the default, and boom! You're free to put a gigantic floppy anus on display for the world in glorious, larger-than-life LED.
And this isn't an isolated incident. Back in 2010, downtown Moscow traffic came to a standstill when a giant billboard displayed hardcore porn and drivers found themselves with a sudden shortage of hands for driving. More recently, a public billboard at a bus stop in Sweden displayed a continuous porn feed as a group of men huddled in close to watch (but not too close, because that would be weird). More recently, a hacker known only as Johnny Cockring used the aforementioned default credentials to hack into two Alabama billboards and upload Photoshopped images of then-presidential-hopeful Marco Rubio in hardcore gay porn:
Scads of Alabama commuters are still unconsciously humming "Y.M.C.A."