"The "NO EATING" rule is a bit absurd, though, considering there's a food stand in the station."
Food is allowed in the station. However, BART does NOT allow food on the platforms, nor in the trains. It is plainly marked "no eating past this point" at the ticket gates. Everyone who rides BART on a regular basis (like the dude in question) knows this.
"Hurting a cop's feelings has never been ruled a crime in the US."
Verbal assault is just as much a crime as physical assault. Note that the charge of assault was never written up, nor was the charge of resisting arrest, nor the charge of not cooperating with the officer in the performance of his duties (all of which are crimes); he has just been cited for eating on the platform. Instead of jail time, he's facing a $250 fine. The belligerent scoff-law got off easy.