stuff like that sucks. I hope is wasn't a Utah fan who did it. If it was, they are not ones I would claim.
I have been going to Utah games for 25+ years and have been through the bad and good times. We have a strange element to our fan base but the vast majority of fans I have seen and currently associate with are not BYU haters,or at least nowhere near the point of taking any physical action and certainly not valdalizm.
Regardless of who is doing it, I am sorry it happened to your car.