I'm not sure what's wrong with a 'symbolic form of cannibalism', to quote Susan's phrase. Popular culture is full of stories about serial killers and rape and God knows what, and fairy stories are notoriously gruesome. Grimm's tales contain mutilation, incest, cannibalism, and infanticide. There are lots of interesting explanations as to why we seem to like such primitive images, but anyway, we do.
I suppose that the literal sense of the eucharist, that one is literally eating flesh and blood, is hard to swallow (!). As to what these things mean, I suppose it's to do with incorporation, merging, taking in the divine, and so on.