I didn't see where all the BYU gear was thrown away or burned in a bonfire, just that they started wearing Utah gear. Every school (or grad school) I or my brothers have gone to, my mom and dad have been excited and wanted a shirt or a hat or something from there to support me. And it hasn't mattered whether it was being accepted at Oxford or my brother being accepted at a local community college for a nursing program - they've been excited and shown their support for us. That includes occasionally repping an article of clothing for that school.

And honestly, I think that's awesome of my parents.

I'll be the first to say if they turned against BYU and destroyed or refuse to ever wear it again, that's probably not the best, but I'm all for supporting a kid who is excited. There's other unknown factors obviously, but that fundamental support seems a good thing to me.

If the kid is the first in the family to go to college for example? Absolutely you get excited about that college, no matter which it is.
If the family ties to BYU weren't that deep beyond "Well we're members so I guess we should support BYU" then you get excited.
If the parents or older siblings are BYU grads, then yeah the turn to supporting Utah is obviously a little less pronounced. But regardless, I'm still going to show support for the kid in any way I can and want their school to succeed in every way that is important to my kid.