Recently I shared my conversion with a couple of protestant friends and they responded that they were happy for me and the joy the Catholic faith gives me. I appreciate the sentiment and their kindness, but it shows a tremendous lack of understanding of their Protestant and my Catholic theology. Our faiths, on a few levels, are incongruent. No Christian who understands their own faith should be happy when one of their own (Protestant or Catholic) moves to the other side (Protestant or Catholic), no matter how much joy it gives the mover.
The Eucharist is the source and summit of the Catholic faith. The Eucharist IS Jesus. It is really, really Jesus. In John 6, Jesus says, "The bread which I shall give for the life of the world is my flesh." He continues, "Unless you eat the flesh of the Son of man and drink his blood, you have no life in you; he who eats my flesh and drinks my blood has eternal life, . . . For my flesh is food indeed, and my blood is drink indeed. He who eats my flesh and drinks my blood abides in me, and I in him."
Repulsed, disciples began leaving because of his claim. He let them leave; he didn't try to persuade them to stay by saying, "Friends, I was speaking metaphorically." No, he meant exactly what he said: The bread and wine were his body and his blood. He said to the remaining disciples, "It is the spirit that gives life, the flesh is to no avail; the words I have spoken to you are spirit and life." Here, Jesus is saying that only by the spirit can we accept this mystery. In our flesh, our reasoning and thinking abilities, we cannot accept this truth. It is a spiritual thing; one that we can only understand by the spirit. And after saying that, more disciples left. They didn't leave him because of symbolism or metaphorical language, they left because they knew he was speaking literally. If he was only speaking symbolically or metaphorically, he would have called his disciples back when they left, don't you think?
This, the Holy Eucharist, is the greatest difference between Protestantism and Catholicism. And this is the crux of what I mean when I say it's poor theological understanding for either a Protestant or Catholic being okay with one of their own going to the other side. A Protestant does not believe that the bread and wine is anything more than bread and wine; it is merely a symbol of Jesus' body and blood.
A properly catechized Catholic believes the bread and wine are transformed into the body and blood of Jesus in the Eucharistic prayer. A Catholic's purest and highest form of worship is eating and drinking the body and blood of Christ. Catholics worship the consecrated bread and wine as the Real Presence of Jesus. When a Catholic leaves the Church for a Protestant church, a fellow Catholic should fear for the mover's soul because they are leaving the greatest gift Jesus gave us, his body and blood in the Holy Eucharist.
But if it's not the body and blood of Jesus, as a Protestant believes, he should fear for the soul of a Protestant who converts to Catholicism as the new Catholic is going to be engaging in idolatry as they worship, what a Protestant believes is, a mere piece of bread. No Christian should be okay with another Christian engaging in blatant idolatry.
Again, while I appreciate the sentiments of my Protestant friends who were happy for the joy I've found in the Catholic Church, they shouldn't be. Admittedly, prior to researching the Catholic faith, I didn't know Catholics believe the communion bread and wine are the Real Presence of Jesus. Perhaps my friends do not either. But if they do know about our belief in the Real Presence of Jesus in the bread and wine, they need to ask themselves why they reject belief in the Real Presence of Jesus in the Eucharist; if they do not reject it, then why haven't they come into the Catholic Church, the only church that offers it; and, if they can explain why they reject it, why could they ever be happy about me finding happiness in worshipping a "wafer"?