Another thing that the original comic misses is that being fat visibly triggers an instinctual assessment that the beast is self-destructive and thus will drag down the "tribe" by being needy, greedy, and lazy.  For the other "vices" in the comic, it is usually much more hidden (because of shame, mostly deserved, and because there aren't as much outward physical signs).  FPH is just an outgrowth of how pervasive fatness is and how it is harder to avoid day-to-day than the others.