Zoe:
My assessment of Protestants’ views of Mormons and Jehovah’s Witness is widely held. The main reason is because neither group has orthodox views of the Trinity and the nature of Christ. Those two related doctrines are the key ones on classifying whether or not something is Christian.
While on the topic, let me go on the record here with something that may be unusual for a conservative Christian theologian: while I don’t agree with their theology, I don’t believe that members in those groups are automatically “not saved.” In the bible, perfect orthodoxy is not stated as the requirement for salvation; living faith in Jesus is. I am sure there are many in those groups who would claim to have just that.
(BTW, y’all, while I’m writing all these things, please don’t think I’m going around criticizing and judging everyone all the time. I learned at seminary, from observation, that that is the LAST thing you do if you want to be useful in any way for the Kingdom of God. Part of the job of a systematic theologian is to distinguish, to classify, and to decide. Theology is the “second tier” of Christian studies. Bible scholars raise up a lot questions; theologians are supposed to make decisions and answer those questions. I read about the beliefs of Catholics/Orthodox/Calvinists/Lutherans (fill in the blank) and go, “Cool, they believe that for these reasons; this is what I think about that, and these are the areas in which we differ.” It is one thing to acknowledge disagreement over something. What you are going to do about it is another matter entirely. In my mind, it is better to try to understand diversity than pretend it doesn’t exist.)
Regarding Protestants and Catholics on the authority of Scripture and Tradition: this is common knowledge. One of the main cries of the Reformers (like Calvin & Luther) was, “Sola Scriptura” or Scripture alone. Catholics believe that besides inspiring the Scriptures, the Holy Spirit has been with the Church throughout the ages, leading it into truth and never ultimately into failure (Matt. 16:18).
O.k., I got a cite, from the very excellent The Christian Faith in the Documents of the Catholic Church, edited by Jacques DuPuis, S.J., from the Council of Trent: “[The Church] receives and venerates with the same sense of loyalty and reverence all the books of the Old and New Testaments—for the one God is the author of both—together will all the traditions concerning faith and practice, as coming from the mouth of Christ or being inspired by the Holy Spirit and preserved in continuous succession in the Catholic Church.”
(BTW, this book—I have the sixth edition, the ref. is from p. 96—is fabulous. Arranged in the standard topical order of Christian theology, it presents the major statements of the Councils and Encyclicals, in chronological order, that relate to each topic. It is a very easy way to get a handle on what the church has believed through the ages.)
I’m sorry if I left out information in previous posts, but I don’t want to turn each post into a book, so I am simplifying things. For example, I realize that only the Pope’s pronouncements made ex cathedra are considered infallible, and I think this has only happened twice. Also, I see a lot of value in reasoning behind the Catholic view of tradition, but to go into detail about all of that would again turn into a book. The question in my mind, and in that of many Protestants, is how a later tradition can be used to overturn the teachings of Scripture, for example with the issue of the mandatory celibacy of the clergy.
Finally, regarding images, I echo what FriarTed said (except about Catholic-Protestant tensions; we get along well here.) Where I live, it is very easy to slip into idolatry, and I see a lot of Christians, not just Catholics, do just that. With the strong biblical prohibitions on that, I do see the use of images as spiritually dangerous and an unnecessary stumbling block.