I'm partial to this kind of explanation
The Religious Motive
Then Moses said to Aaron: “come forward to the altar and sacrifice your sin offeringand your burnt offering, making expiation for yourself and for the people, and sacrifice the people’s offering and make expiation for them, as the L-rd has commanded.”Aaron came forward to the altar and slaughtered his calf of sin offering.(Leviticus, 36: 7-8)
Sacrifice in the Hebrew bible proceded prayer as the means by which humans connectedto G-d. In spite of the inevitable trespass, through the religious ritual of sacrifice, humans were able to feel purged of sin and pure enough to stand before their Creator. It is the underlying contention of this paper that the process of guilt purgation constitutes the fundamental religious motive in all humans.
The cycle of guilt/sin—sacrifice—redemption is a drama that occurs within the individual psyche of a human, or, often tragically, the drama can be played out on the sociological level with whole societies acting out a collective religious need.
In Leviticus, the ritually pure high priest sacrifices the perfect vessel (calf, goat, birds,etc.) so that the individual or people can atone for their guilt. The priest casts the collective sins of the people onto the ritually pure goat.
Psychology teaches that individuals project their inner tensions and conflicts onto external vessels to assuage their psychic tensions. Demagogues exploit the resources of language to manipulate vulnerable masses of people to accomplish their goals with rhetoric that exploits the human symbolic need for guilt purgation.
Thus, the religious motive can be described from three different aspects of human behavior: the religious, the psychological, and the rhetorical. Psychologists call it projecting while religions use the word scapegoat. Both terms, projection and scapegoat rely on the human capacity to identify like with perceived like.
http://64.233.169.104/search?q=cache:iM9Kwm8CV_gJ:www1.yadvashem.org/download/education/conf/Zimmerman.pdf+projection+scapegoat+bible&hl=en&ct=clnk&cd=4&gl=usI don't know much about this source but this is essentially the basis of Christianity and many older myths, a someone sacrificed for the sins of the community, so that they can be relieved of guilt. Ancient human tradition, when you couch it in non-religious terms like projection it becomes even more pointless and sad, but it's still the same bag o' chips. (I don't know anything about that source I just liked how he expresses it).