There isn’t much meat on a demon.
Not that you’d ever want to eat one. Unless circumstances warranted it, you understand. Or if, say, you just really, really felt like it—one should live and let live, after all. But trust me, they are skinny and beyond that, if the Ledger is to be believed, it’s clear they weren’t designed to be predated (or scavenged), especially as they are themselves quaternary in any food chain.
It’s a well-documented fact that humans thrive best on primary and secondary food sources. In other words, vegetation and herbivores. During drought or famine, survival dictates these rules be bent but that doesn’t make snake meat tasty or tiger steaks healthy.
Demon flesh is a definite no-no.
Cogitate, if you will: primary blade of grass eaten by secondary cow eaten by tertiary human whose misery, fear and/ or heart and liver are eaten by quaternary demon. For a human, eating a demon would qualify the human doing it as quinary in the food chain. As well as making him very ill. If a demon ate another demon, it too would become a quinary source of food (as well as being classed a cannibal).
According to the Ledger, it’s not uncommon for demons to eat each other, so by that logic, if a human was, by chance, to eat a cannibalistic demon he or she could then be considered the senary participant in the food chain.
The food chain’s a lot longer than people think.
There are a few umpteenary beings, as I understand it; the kind of creatures that eat entire planets and ecosystems, but if you ask me that’s gluttony.
Anyway, the point is this: demon meat is about as healthy as a skunk dung soufflé.