I have no idea how much it costs

Nor the ROI, or how it would be calculated.

To hazard a guess as to a response to 3), it would probably be an affirmative case that diversity, equity, and inclusion are consistent with Catholic values. I suspect they’d say that DEI (at least, as conducted at Notre Dame) is rooted in, and furthers, the inherent dignity of all people. DEI is consistent, with, not at odds with, Catholic teaching. I don’t think they would agree with the premise of your last paragraph. They would probably say that DEI acknowledges differences, yes, but that such differences can enlightened and benefit society as a whole.