As a Lutheran, I can say that as far as the branch of Lutheranism that includes the church I attend (ELCA) we believe in the entire Body of Christ - and that includes Roman Catholics. We work with the Roman Catholic churches in our area to help the needy and the poor, to fight against violence, and to bring others to God however they will come. We believe there are many more things that we have in common with Roman Catholics than we have with non-Christians, and we are all part of the Body of Christ. Our Creed includes the line “We believe in the Holy catholic church,” which refers to the worldwide body of Christians, not just Roman Catholics.
But I must take some exception to the condescending comment by sainteriksrose, which suggested that Protestants are only partially authentic Christians. If you recall from Scripture, Paul was extremely clear about the fact that the churches he started were CHRIST’S churches, not his, not Apollonius’, and not of any the others Paul ordained. I am aware that certain Lutheran groups are just as guilty as other denominations when it comes to thinking we have it “right.” But the fact of the matter is, Jesus never felt the minutia religious people seem to worry about was all that important. I believe in a God that is accepting of the many ways his sheep come to him, as long as they come. If you happen to follow 2000-year-old traditions like the Catholics or 500-year-old traditions like the Lutherans, or 20-year-old traditions like another denomination, I doubt God cares so long as you worship Him in a manner that is respectful (by the standards of your culture), sincere, and is based upon Scripture. Most Protestants and Catholics have more in common than you might think if you have never studied the other. What we disagree about is usually rather unimportant and silly.
What about Peter’s church? Are Eastern Orthodox folks less Christian? if so, it has nothing to do with the fact that they aren’t Roman Catholic. At least Peter actually knew Jesus, so I would say that they have a leg up on the Catholics, if we are keeping score like that. See how silly this becomes? We are all the body of Christ, so we should always try to act like it and be gracious to those who worship in a different way or who came to Christianity differently. Peter, Paul, Constantine, Luther, it doesn’t matter as long as we come.
What I find even more disgraceful and disturbing is how so many Christians (both Catholic and non-Catholic) hate Jewish people. I will never understand that because, like it or not, the Jews are God’s chosen people, and the gentiles didn’t get invited to the party until thousands of years later. So everyone should thank the Jews for being there to give us Jesus Christ, not be angry that their misguided leadership killed Him. That was the best thing that ever happened to us.