While UM/ND was a rivalry, it wasn't hostile until the Nov 30, 1985 game.
ND had hired a HS coach Gerry Faust and this was his last game after five years that went from mediocre to bad. Everyone knew Faust would be fired after this last game, but ND and college football decided he was a "good man" and should go out with class.
The color announcer was Ara Parsehgian who had been ND's (successful) head coach prior to Faust. Parsehgian was a ND man through and through. He decided after a certain UM lead that was enough and UM should just quietly run out the game so as not embarrass "good man" Gerry Faust. And Parsehgian viewed ND as an institutional icon. He thought ND was the center of the universe and should always be viewed with reverence.
Jimmy Johnson didn't agree and ran up the score 58-7

Parseghian went ballistic, which was hysterical to us. And all the proper people in college football criticized JJ and UM. It ****ed all of them off more when JJ went on TV and said he didn't care lol
That's when the hatred started