Why do some Fundamentalist Christians believe Catholics are going to hell?
The mainstream way of looking at it is there are Catholics, and there are Protestants.
Both are Christian. Within the Protestant group, you have your Pentecostals, Baptist, Assembly of God, Methodist, certainly Lutheran, Church of Christ, all these different mainstream denominations, Faith Free Evangelical.
The Protestants believe in one Central truth, and that is that Jesus is the son of God, died on the cross at Calvary for our sins, was resurrected three days later after fighting Satan for the keys of hell and death, and now he sits at the right hand of God interceding on our behalf when we pray through Jesus to get to God.
Protestants believe that we need to acknowledge to God we are sinners, ask Jesus to come into our lives to be Lord and Savior, and that's pretty much mainstream agreement.
Where the difference is, and this is where people on the outside looking in think that all Christians do is a bunch of in fighting because we can never agree on anything.
Most Christians agree that main Central truth of which I just stated above. Where the difference is that some will celebrate communion every week, some once a quarter, some believe you need to be baptized to be saved, some believe you don't need to be baptized to be saved.
Some speak in tongues, some don’t.
There's all these differences of worshiping, because most churches in the Protestant denomination are autonomous, meaning they don't have a hierarchy to answer to. Locally on their own they decide how they're going to run their own church and how they are going to worship.
Most even search for, interview and hire their own Pastors.
The Catholic have common ground with Protestants in that they believe that Jesus is Lord also, born of the virgin Mary and died on the cross for us.
Of course they have the Pope.
Their differences come in where they believe that you must be baptized to be saved. They believe that after you die, that your relatives can pay a priest to pray for that person's soul, and if they weren't going to heaven when they died, they can go to heaven if the priest pray’s their soul into heaven.
That it is a huge different with Protestants, because that totally negates the cross.
Catholics also tend to put Mary the mother of Jesus, Peter, John, and Paul way up there on the scale of importance, so much so that they pray to them.
Protestants believe that we only pray to Jesus.
Several other differences but I can only have so many characters for each post. Questions just ask.