I live in STL.
The number of Catholic parochial schools here is very very high. Notre Dame is like the default team to appreciate for anyone who didn't go to Mizzou or didn't go to a power 3 school. And even then, if you went to say, Vanderbilt, you would be at least a part time ND fan. And since SLU has no football team, they cede a lot to ND.
And it's not a rabid fandom. Which is almost worse. It's just sort of like and expectation to appreciate them. If SLU even had a poor FCS team, it would be more tolerable around here. So, when someone around here finds out you don't like ND, they will actually question you. Like "Why do you hate them?"
My answer?
"Because they're not Iowa. I hate every team that isn't Iowa. You should ask me how I feel about Nebraska."
I do point out, that ND gets way more love, attention, and hype than they deserve. And the more unrequited hype you get, the more I will hate you.