Its a diabolic corruption of Old Testament Animal Sacrifices (where the victims were either killed humanely and then eaten by the priests, or let back out into the wild after the sins of the community were symbolically transferred on to them). Nowhere in the Old Testament does it mandate such a cruel form of animal abuse, and its actually impossible to perform the OT sacrifices because of the lack of a Temple (and the fact that Jesus' death on the cross and daily sacrifice in the Eucharist is the only sacrifice that can actually atone for sins).