The ritualized cannibalism bit is transubstantiation, the belief that the blood(wine) and body(bread) of Jesus turn into his real blood and body during consecration in catholic mass.
But you could make a dig into it overall just beacuase the bread and wine are symbolic ritual cannibalism, very culty sounding when you look at it from another angle.
Communion is not really just a catholic tradition, and it is not a wild interpretation to make when a dude says these 2 things sybolically represent my flesh and blood, calling the whole ritual symbolic cannibalism is not a stretch.