I don't think that's the problem. I think it's more that these oversweetened chocolate box collections misrepresent the wider repertoire, and trying to hear some greatest hit in its context and in its unsweetened form is like then being told to eat your greens.
He also had a duet from Monteverdi' Poppea on something which he particularly liked and I tried to gently build on that with a collection of Monteverdi duets with Kirkby and Tubbs, but that too was a nonstarter.
He lost interest after that and I knew better than to keep trying, even gently.