There's not an example in real life because we know no other sentient species. I'm fairly confident that if we did, we'd consider it cannibalism, or have another term for it and consider it equally vile.
Of course, that ignores the oddity that its even possible for life forms that evolved in different solar systems over hundreds of millions of years to draw nutrition from each other's flesh.
Ahh, ok, there's one exception and I don't doubt that there are more. However, would you agree that most times it is considered cannibalism though? Hmm, exceptions most commonly exist in the case of entities that are considered monstrous and worthy of destruction by their very nature (like vampires and such).
Certainly it is almost unheard of for it to be considered all that different in terms of how horrific it is. Imho, most people agree that there'd be something vile about eating something you could have a conversation with.
More to the point, I don't think the TES universe makes a distinction between one race eating another and one race eating a member of the same race -- well, super-extremists might, but not the average person in the TES universe.
Edit: As for the oddity, it might not be that odd given how common amino acids are, which naturally enough combine into proteins. For all we know most or all life isn't so different from ours. Granted, this would be less interesting that other hypotheticals, but the universe is sometimes a bit boring that way.

...not crazy about 'testing' the Giant's Toe or the Troll Fat either. 




