They are simply not fans of BYU. That's completely okay with me if they are a fan of their alma mater or some other team for whatever reason - there's nothing about their faith that is diminished by that.

But in some respects I agree with you, that when they turn to BYU bashing it's a little different (especially for me as a BYU fan). I don't rip on other schools and could pretty much care less about them (okay, maybe the Yewts a little). To me those BYU ripping LDS faith fans are similarto a LDS politician who would support abortion, gay marraige and other specifically doctrinally opposing beliefs to those of the church.