A rivalry by definition is competition for the same objective or by superiority in the same field.
Utah is now in PAC12 BYU is not so both are not competing for the same objective. Utah is winning the series something 61-34-4 or 61%. Again Utah leads the series. You win by 1 or 50 a win is still a win. If it was a rivalry they would both be winning by 50%.
So BYU fans can claim it is a rivalry if Greg Hughes had not forced Utah to play BYU or be audited Hill was dropping the series. BYU needs this game more then Utah does. Look at this coming weeks tickets prices being charged by BYU. The fact BYU returned over 1500 of their allotted tickets and Utah sold them to their students.
So tell me why shouldn't Utah fans not call this game a rivalry game?