It may shock some to know this, but the scriptures say that Christ came to bring division....
Matthew 10:34-35: "Think not that I am come to send peace on earth: I came not to send peace, but a sword. For I am come to set a man at variance against his father, and the daughter against her mother, and the daughter in law against her mother in law"
Christ brought truth into this sinful dark world. The truth is not in unity with lies. Where there is truth there will be the opposition to the truth. We're in a spiritual battle. Jesus said the truth would cause division among family members, among people we know, because some will believe the truth and others will accept the lie. One is born of the Spirit and the other is not, so they are unequally yoked. The scriptures speak about the two sides - the narrow and broad road, the wheat and tares, the sheep and goats. One is on God's side and the other is on the enemy's side. So there will always be a spiritual battle between the two sides.
Not all who call themselves Christians are born of the Spirit. On judgment day many will say "Lord, Lord," but He will say He never knew them, because they were never His children. Not all Catholics are born of the Spirit, just as not all 'protestants' are born of the Spirit. I've read testimonies of many ex Catholics who were saved and then left that church, because they could no longer partake in something that doesn't agree with the truth of God's word.
There is one true gospel, not several. There is the truth and then there's the lie. There can be no fellowship between the two.
Catholicism is not a christian denomination, it's completely separate. For the most part, the various christian denominations are in agreement on the same one true gospel but just differ on non salvational topics (like the end times, etc). However, Catholicism does not teach the one true gospel, so they are completely in opposition.
The ecumenical movement is a rebellious movement. It's the unity of all false religions, with the goal of peace and unity, regardless of belief or doctrine. It's just like the tower of babel all over again, where all were uniting in rebellion against God.
So when it comes to discussions here, the truth must be shared. Many find it difficult to see anything beyond a personal attack, but it's the systems of lies that are being exposed.
Many on here are knowledgeable with Catholic doctrine and not making wrongful assumptions. Some are ex Catholics and have families that used to be Catholics, some have attended catholic schools and churches in the past, some have read through the catechism and see all the errors and how the catholic church system greatly deceives the lost, though the leaders also are deceived themselves.
Just a small section of the Catechism says... there is no salvation outside the Catholic church, but that Muslims are saved because they acknowledge the same God. It says that Muslims and Jews will be saved, despite their rejection of Jesus as savior, and that the ignorant (who have never heard the gospel) can do God's will through the dictates of their conscience. But they repeatedly say that born again bible believing Christians who know and accept Jesus Christ as their savior (through faith alone in Christ alone) who do not submit to the Church of Rome cannot possibly be saved!! In their various statements they are claiming that Jesus is not the only way of salvation (839/840/841/846/847/Canon 9 - examples)