twenty years ago, maybe. So it was a while back. But we were there to cheer for the Rebels because they were playing some other team in the conference, not BYU. We were wearing as much red as we could find (that wasn't much since there just isn't much red in our wardrobes) to support UNLV, but my brother made the mistake of grabbing what happened to be a BYU hat on his way out to cover his unkempt hair. It was a navy cap with the cougar on top of the letters BYU, which were in tan. It was a decidedly ugly style BYU hat, but certainly not a loud declaration that that's who we cheer for. It was not meant in any way as a statement. It was just an oversight.
Our seats happened to be right by to the student section. While walking in, one of the Rebel student fans noticed his hat and pointed it out to others. Soon, he had the entire student section booing him (this was while the game was going, by the way. Yeah, we arrived a little bit late) and there were people who were throwing stuff at him. He took it in stride, and we took our seats assuming that the student section would eventually like to watch the game that they all came to see.
The harassment did not stop. They seemingly did not even care about what was going on in the game with the team they supposedly cheer for. There was continuous screaming, and bombardment of various and sundry items: chapstick, dirty napkins, ice, etc. Eventually we decided to leave because it was just too ridiculous and distracting, and security wouldn't do anything because it was too difficult to see any particular person launching projectiles. It was various people constantly from the student section. Why? Literally his only provocation was wearing the wrong hat to a game in which we were going to cheer for the Rebels, in a game that did not involve BYU in any way.
Despite being a Las Vegas native, he has never cheered for UNLV in anything since then. I still sort of do, half-heartedly, when they are not playing BYU or a Big XII team. But I certainly recognize what a low class fan base many UNLV fans are.