I’m not sure you’re going to find it possible to get a definitive answer to your question. If you were to ask the same question of the present-day USA, you would most likely get different answers depending on who you asked, what agenda he/she may or may not have, and the context of the asking.
RR
. . . but if Metzenbaum identified himself as a Democrat yet consistently voted Republican in the Senate and in every election, I think anyone would be justified in questioning whether he is, in fact, a “real” Democrat.
RR
You’ve confused Metzenbaum with Lieberman. All those yarmulkes look alike. 
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???
I’ve never actually encountered that claim. I remember when they changed from “damned heretics” to “separated brethren” in the mid-1960s, but I don’t think I have encountered a Catholic who claimed Protestants were not Christian. (Certainly a claim of “substantial number” needs a bit of clarification.)
I recall the mental contortions Sister went through before admitting Protestants were Christians, though still the worst sort of devils. It’s one thing to not know the Truth because you’ve never been exposed to it, like the Pagan Babies we used to buy, but something much worse to deny it when it’s as plain as the nose on yer damned, heathen face. 
Hmmm, buying Pagan Babies has potential as a Pit thread someday.