In Murray Sperber's history of ND football I recall Michigan being at the forefront of the anti-Catholic force that included Northwestern and Chicago which essentially banned ND from playing the big boys in the Big Ten.
But what I really want to say in defense of BK is that I went to ND from '63 to '67. We were national champs our senior year. I like to think that wasn't that long ago. And there was NO RIVALRY with Michigan. I took my new wife to see the Irish play MU in '81 (one of the best college games I have ever been to) but this supposed rivalry is only a few decades old whereas USC, Michigan State, Navy, Purdue - those have been around for much longer and while, for example, Purdue and Navy have not produced dramatic games in recent years like ND - Michigan, I can assure you they used to.