Pigs are like humans in that they will eat just about anything. When I lived out in the bush we had pigs that were turned loose to feed off the forest. They were about as organic as meat can get. They tasted like it too.I've often suspected that's the explanation, it comes down to, knowing what a pig will eat, would you eat a pig? Lot of people say no. Pigs also carry some pretty nasty parasites, like trichinosis, and no doubt it was noted that some people who ate pig got very ill or died horribly.
BTW: cannibals call humans "long pigs" for a reason. Would you eat a human knowing the kind of crap they eat?