Bronco was easy for Ute fans to dislike. I remember back in the early 80s - Frank Arnold was BYU's basketball coach. He was also easy for Ute fans to dislike. I have not disliked a BYU basketball coach since then.
As a Utah fan - I despised Danny Ainge 43 years ago (not now). He was arrogant and cocky. BYU fans loved him - as they should because he was a great leader for the Cougars. When an arrogant guy is our guy - he is great. When he is attached to our rival - he is terrible.
So, your point is very valid.