Having grown up in SLC, surrounded by U fans, it's your very statements that gets LDS UofU supporters upset--your statement assumes that if they are LDS, but go to the U it's because they couldn't get into BYU, rather than actually choosing to go there because of family traditions, it's cheaper because they can live at home, or they just grew up rooting for them.
Jon Huntsman is as good as you get and you see him front and center at the U games dressed head to toe in red, so did his family; it's not because they couldn't get into the Y. I'm sure you don't really believe that's the case, but enough Y alumn state that reason that it get's they're ire up, which is why it's fun to say it.
So they think BYU fans are very arrogant and pridefull and think they're better because they went to a church school.
I don't agree with the sentiments and have similar questions how you physically loathe BYU and be in good standing--I have no patience for it and is one of the reasons I'm glad I don't live in UT any longer because I don't have to deal with that every time we play.