The Catholic Church supports three baptism’s water, blood and desire.
Let me focus on desire
If the Protestants only knew they would all come home to the Catholic Church.
I personally believe that when God hardens our hearts so that we might not believe that is a true blessing, because on the last day when our works are tested by fire, perhaps God hardening our hearts will protect us when all of our good works and sins are revealed.
Now that being said not every one who calls the Lord Lord will be allowed in. Perhaps as some of these Christians fall away from the true teachings of the Church and Jesus they endanger their salvation.
Please note that even Catholics who slip away from their faith, or become liberal in their ways will endanger their salvation.
Some will be held to higher standards, Christians will be held to more strict standards than the other who had another religion but never heard the good news, Priest will be held to a higher standard than us lay people because they have a higher authoritive postion as Shepard of the flock and for the men who knowingly lead the people astray I feel sorry for them.
The good news is that we are not the ones who judge, we are just the ones who are commanded to love, and if we look closely at the Lords prayer, we ask for our sins to be forgiven as we forgive others who sin against us, we use the term tresspass but we are truely talking about sin.
We are all sinners and as we all slip away from our faith or from the Church, or even realize later that maybe we too have been caught up with the world and have fallen in a much different way, we as Catholics have the fortunate blessing and gift to fall back to the Church for guidence, repentence and to get back God’s grace.