Let them cheer for their team. And if BYU wins how about be cool about it. And if lose more gracious.
Yes this is anecdotal and I was told most fans were great, but I have a neighbor who is an SC fan. Raised in SoCal. Their team for decades. Went to the game. After BYU won some idiot got in their face about it.
If you can’t handle the opponent having fans in LES to cheer their team on, you need counseling. Just let them do it, as you would want to be able to cheer for BYU in opponent stadiums without their crowd up in your business.
Don’t be THAT guy.