Your second statement is the most troublesome to me, namely that “rejection of one necessarily means rejection of the other.”
I would prefer to concentrate on the union part, rather than the dis-union part of the discussion.
In my earlier post, I was trying to make that point. I used the “pause” part because what I was imagining was that you would stop and think about the first part—that of fully accepting Christ; because that’s what is important. The comment about rejecting was meant to be secondary. I suppose it did not come across that way on the screen.
Do Catholics sincerely believe that if Protestants reject the Church, they necessarily reject Christ, and thus G-d?
Yes. We cannot make a distinction between Christ and His Mystical Body (ie the Church).
To accept Christ (fully) necessarily means to accept His Body.
However, having said that, I want to say that I answered you because you asked. A further explanation is needed. That will come next because you’ve already started to answer it yourself…
Could it instead be that the union with Christ is incomplete, partial, or faulty rather than rejected or nonexistent?
Yes, it could be. The two are not mutually exclusive. What I would like you to keep in mind is that
“rejecting” Christ is not the same thing as not-being-introduced to Him. To reject something is an action, a choice. It is not the absence of an opportunity. Every person is different, and thus everyone’s introduction to the Church is likewise going to be different.
In other words, the phrase that you wrote in your question was “if Protestants reject the Church…?” is not the same thing as saying that “all Protestants do reject the Church.”
One could ask me “if a Protestant jumps into the ocean, does he get wet?” the answer would be clearly yes. But that does not mean that I am saying that all Protestants do jump into the ocean. I hope you see the difference, because I answered the question the way you asked it.
On the one extreme, some will reject the Church–to their own condemnation.
On the other extreme, some will never even hear about the Church; they cannot reject what they were never given the opportunity to accept, and for them, the infinite mercy of God still has a place for them.
Most (of those you’re asking about) will fall somewhere in between those 2 extremes.