This is my body, this is my blood.
And arguments will reign over exactly what Jesus means here until the cows come home.
Be that as it may, Metatron, you're just rehashing an ancient Roman accusation against Christians.
We do not gain Christ's holiness by eating His body and His blood. He has promised that as
partakers in this remembrance of Him, He will be present with us. The rubrics of the Church of England, for example, allow that someone who is unable to physically receive the elements is nonetheless a partaker in Christ's Body and Blood. Similarly, one who receives physically but does not do so inwardly is
not a partaker in Christ's Body and Blood. Because of possible superstition about the elements in former days (which would be directly analogous to your cannibal analogy), where the elements were used, for example, to cast spells or ploughed into the ground to attempt to increase fertility, the rubrics also require that all the remaining consecrated elements are consumed by the priest after communion. The elements are not magic talismans.
Nevertheless, there is something to be gained from your comparison in the OP. Religion generally, and Christianity just as much, are full of allusion, symbolism, metaphor and so on. The idea that by eating something one gains something of the nature of the thing eaten is a common concept throughout humanity. Why not draw on that common human concept to illustrate spiritual feeding by God?
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