The question is posed, and then answered, by  Jonathan Harrison, former chair of Philosophy at the University of Nottingham, UK, in his online essay “Is Eating People Wrong?”
The professor points out that -

“Animals that can be eaten are often better taken care of than men, whose artificially induced inedibility provides those responsible for them with no such incentive. “

That said, however -

“I would not be in favour of individuals eating people in contemporary bourgeois society, as this might well interfere with regulations for the hygienic disposal of human bodies…”

Though with the observation -

“Perhaps it is my age, but I myself, like the older cannibal, am not able to see what is wrong with eating people.”

And not forgetting that -

"Children, unlike pigs, do not grow quickly enough to make farming them an economical proposition - though if cannibalism really had been necessary to mankind, it is possible that some human children might have evolved to have been quicker growing."

But with the proviso -

“I must confess, however, that I have never myself eaten anybody, even in the interests of science.”

BONUS also see: Harrison, Jonathan. “Dr. Who and the Philosophers or Time-Travel for Beginners.” Aristotelian Society, Supplementary Volume 45 (1971): 1-24. which can be found in Time-Travel for Beginners and Other Stories (page 51)