ESPN recently dubbed the BYU - Utah rivalry as the #1 non-BCS in-conference rivalry in college football.
Even with all the qualifiers in that distinction it is arguably one of the most passionate rivalries in all of college football primarily because of the added element of religion. For those who are unfamiliar with the background you can get the full history in some very extensive Wikipedia articles on the general rivalry as well as the "Holy War" as it is known.
The rivalry is full of culture and color in and of itself but in this forum I would like to look at the elements of LDS culture and Utah culture that can possibly explain the ferocity of the rivalry.
I think the fundamental reason is demographic. There is a growing demographic divide between the two schools and the surrounding communities, the percentage of LDS residents of Salt Lake City proper has been steadily decreasing since the 1960s while the smaller communities of Provo and Orem remain predominately LDS. As that demographic divide continues I anticipate the religious polarity of the two schools to grow which I think could give greater potential for the rivalry to turn ugly or distasteful.
The second element that should cause self-reflection for Mormons is the threat of pride. I'm not talking about being proud of your team or wanting to win, I'm talking about when winning on the football field falsely gets coupled with self-righteous notions of having a monopoly on religious truth or superior religious piety to the point of haughtiness. This is not a challenge to the Latter-day Saints collectively but individually. Each passionate sports fan needs to monitor themselves that they do not cross that line.
Should Mormons be proud or ashamed that they have a reputation for a unusually fierce rivalry? Does it matter? I would argue that there can be a healthy and fun expression of rivalry and competitiveness in sport but that maintaining that healthy status takes restraint and a sense of humor otherwise it is destructive. As a general principle I would rather see a religious-flavored rivalry played out on the football field rather than in the street with guns, which is still the case in parts of the world.
The question I'll leave you with for discussion:
Will there be sport rivalries during the Millennium?