I understand your logic, and even though I'm obviously not a Sioux fan the way that you and everyone else on this board are, there's a BIG difference between rooting for both the Sioux and the Crusaders as opposed to rooting for the Sioux and the Gophers.
UND and UMN are in constant competition with one another, and bitter rivals. From my perspective, that's like someone rooting for both the Rangers and the Devils. When one wins, it's pretty much always bad for the other, except for a few rare situations. HC and UND, on the other hand, are on completely different levels. Except for our two meetings in the NCAAs, I doubt there has ever been a situation where a Holy Cross win would adversely affect the Sioux.