I think you are missing the point (and certain parts
).
First, primal doesn't mean Neanderthal. It means fundamental or deep-seated -- way down in and integral to our psychological make-up.
Second, because our culture doesn't offer standard "initiation rites" that mark the transition from childhood to adulthood for men (not sure it does for women either), a vacuum is created that groups like fraternities step in to fill.
Third, I think most fraternities, in some way or another, say they are about making better men -- not just gentlemen, but better men. So there is built into the fraternal experience the idea of being the best man you can be. And in some ways on a deep psychological level, being the best man you can be requires proving yourself -- to yourself and to those whom you hope to have accept you as a peer. There is more than a grammatical difference in "joining" a fraternity, as you put it, and "being accepted" into a fraternity.
I'll readily agree that doesn't necessarily line up with excuses to haze. I'll also agree that there is hazing and then there is hazing. My point is, though, that I think hazing started because of this inborn need to prove one's self through some kind of ordeal. We can never successfully get rid of hazing unless we understand the psychology that underlies it and find other, more appropriate, ways to meet that need.