They hate BYU.  They either hate the religion or the notion of an academic institution that tries to live up to religious ideals.  They point at those wearing blue who are arrogant or who engage in name-calling to justify their rationale.  They paint all BYU fans with a broad brush and we should not return the favor.  A majority of Utah fans are not this way.  But there is very vocal minority of religious bigots in the Utah fanbase.