@ampnaman
I would pretty much eat anything not human, if I had the meat.
First, it would be a waste to throw away perfectly good meat of already dead creature. Also, the sentient argument isn't really valid if you already eat cow, horse, deer, stag or boar meat... and many more... they are also considered sentient.
Sentience is the capacity to feel, perceive or experience subjectively.
And we don't know if Orcs are demi-humans (If you consider demi-human as half human/half monster that can reproduce with humans). It's more likely that they are a completely different bipedal species.
As long as he doesn't eat the brains, because of prions, he should be fine.