Dairyewts for generations have watched BYU teams destroy USU teams most years, and not give it or them a second thought. They don't care about how trashy their behavior is towards BYU as long as they get to express that frustration in some way. Religion isn't near the push-button for them that it is for yewt fans, but dairyewts will still use it to try to get back at BYU, hence the Davies stuff.

The SDSU fanbase is basically just made up of Cali-trash. Their school is just one of many second-rate schools that make up their state's second-rate university system. Not much there to be proud of. BYU teams historically got the better of them, but not so much that they'd hate BYU JUST for that. Plus, they've seen a lot of success in basketball the last decade or so, so that gives them a bit of a superiority complex. The missionaries thing is just them not being any more creative than associating BYU with the most typical "mormony" thing they otherwise see. Not on the level of a Stanford Band halftime show, anyway.