I think eating another intelligent humanoid is a chaotic act, not necessarily an evil one. I could imagine a barbarian tribe that believes eating their dead allows the person to live o within them, or that if eating a great warrior gives you some of his strength, a great champion would want to be eaten so his strength could continue to protect his tribe. In this way, eating the fallen is a way of respecting the dead, and wouldn't be evil in my view. Weird, uncivilized, and maybe hard to stomach for some, but not evil.
In this specific situation, I also don't think its evil. Your Half-Orc was scavenging, if it doesn't make animals evil, it doesn't make him evil.