Unfortunately, it was BYU fans after the 2013 game when a phantom holding call negated a kickoff return TD for the Cougars.

I get it, it's fun to vilify Utah fans as the worst (and they've shown some great evidence that it is true) but unfortunately there are lots of fanbases that have shown some pretty poor behavior over the years including BYU. I still remember the first WCC game vs SMC where debris was thrown on the court. I remember being chastised by Elder Holland after the BYU vs Oklahoma St game at the Delta Center. I sadly remember many, many times where I have lost my cool at sporting events and have embarrassed myself, my family, and sadly at times my team and my church.

I guess I just hope that we can do better and be better in the future so more of these videos of poorly behaving Cougar fans aren't posted online.

https://www.youtube.com/watch?v=u3HM9s_eq4c