Sure, for them that might be fine. Take Frank Herbet's
Dune. The fremen would drain the fluids from a dead body and drink them, because water is precious, and the dead don't need it. To us, such a thing would be evil. To them, wasting that much water might be evil, or at least very, very wrong.
I think it was the gauls, they used to throw babies onto the spears of enemy warriors. Why? Well, for starters, it would probably unnerve the soldiers. Nothing freaks you out more than being splattered with baby juice. And really, if the adults were defeated, what hope did the babies have?
In your example, the eating of "flawed" babies, yeah, I can see that. By eliminating the weak or flawed, those abnormalities are not passed on. I mean, modern Western society practices reverse Darwinism - we keep the sick, the disabled and the just plain stupid around, and they often have kids. The human gene pool isn't being constantly refined, it's being kept polluted with morons and people born with a third arm sticking out of their foreheads.
In your example, a baby born with eleven fingers never has children. Eventually, that gene would likely be lost. The same applies to say... a kid born with no legs. Now, that kids gonna go through hell, if he lives. This way, he doesn't live. He doesn't have children. A theoretically infinite number of people don't have to endure a life of torment and ridicule, and the society as a whole is better off for it - it doesn't have to take care of individuals who cannot contribute in the same way.
Is cannibalism evil? Of course it is, you might say. Why? I mean, if it's done out of respect and all, why is it so evil? Some animals do it, and we all know that animals are solidly true neutral
.