If this guy's story is true, then I'm on his side. It pains me to see fellow fans of the show punished for something as trivial as what cartoon they prefer to watch during their spare time. If he really was doing his work and minding his own business, then he didn't deserve to be fired.
I also think that he should find someplace else to work, while also being cautious with what could be revealed to his coworkers. Sure, I myself love ponies, but I make it so that it doesn't seep into my workplace (unless it's music, then headphones should suffice).
Overall, one should be mindful of what he/she has the potential to expose to the public eye, even if it appears harmless to you.