To be quite honest, gays lack tolerance of anything that is anti-gay, so many gays (even BYU grads), esp in Utah, have a negative or develop a negative attitude about BYU....a lot of it stems from disciplinary actions of gays at the Y, the church's stance on gays over the years (including Prop 8), and the history of nonacceptance in the church.
I graduated from the Y in 2000, and I am as die-hard as it gets. I have converted a bunch of my gay friends to BYU sports, and many of them travel with me to games. Of course, they are required to wear BYU gear!