I'm going to ask a few questions I want you to think long and hard about.
1. What is the name for a follower of Christ that doesn't believe in Mormonism?
2. What is the name for a follower of Christ that doesn't believe in the Watchtower?
3. What is the name for a follower of Christ that doesn't believe in Islam?
4. What is the name for a follower of Christ that doesn't believe in Evolution?
5. What is the name for a follower of Christ that doesn't believe in Catholicism?
Of the 5 religions mentioned above, 4 of them are commonly addressed by this ministry, and one of them (the Watchtower), I intend to study more in depth and start addressing it here more soon. The answer to the first three questions is that there isn't a name for that. The answer to question 4 is Creationist, which is descriptive of what we do believe, not what we don't. How is it, then, that there is a specific name for a follower of Christ that doesn't identify as Catholic?
Let's rephrase the first question. What were followers of Christ called before Mormonism appeared? Answer: Christian. Non-Mormon Christians believed the same things before Mormonism existed as they do now. We don't need a special name for our rejection of Mormonism because Mormonism is the new claim. We reject it because we had pre-existing beliefs that it contradicts. We can do the same with Islam and the Watchtower.
Let's rephrase the fourth question: What were followers of Christ called before Evolution appeared? We could still have been called Creationists, because we still believed in the Genesis account of Creation. Once again, we don't need a special name for our rejection of Evolution because Evolution is the new claim. We reject it because we had pre-existing beliefs that it contradicts. The word "Creationism" is sufficient because it describes those beliefs.
So, let's rephrase the fifth question: What were followers of Christ called before Catholicism appeared? The answer, surprise surprise, is not Protestants. We weren't called Protestants because there was no Catholic Church to protest. The answer is that we were called Christians (Acts 11:26).
Just as with the other religions mentioned, we don't need a special name for our rejection of Catholicism because Catholicism is the newer claim. It may have older claims than Mormonism, but the fact remains that "Protestants" reject Catholicism only because Catholicism contradicts beliefs we already held.
This much is made evident by the doctrine of "Sola Scriptura". Sola Scriptura (Scripture Alone) is the doctrine that the Bible is the sole and sufficient authority in Christianity (2 Timothy 3:15-17). Sola Scriptura, which itself can be defended exclusively by scripture, is effectively an appeal to the oldest Christian source. Even Catholics that claim the Bible was not officially canonised until the end of the 4th century must admit that it was written in the first century, by the very Apostles they claim to respect, and inspired by the very God they claim to worship. Because of this, any doctrine we find in the scriptures must be an original and authoritative doctrine, and any doctrine that contradicts the scriptures must, therefore, be incorrect.
The irony of this is that while "Protestants" rely on Sola Scriptura, and thus none of our doctrines are even remotely affected by the existence of Catholicism, Catholics utterly reject Sola Scriptura as a "Protestant" doctrine, both adding to and rejecting the scriptures in many ways, some of which affect the Gospel itself.
To my Catholic readers, I have a challenge for you. Complete the following sentence: Protestants believe...
By definition, the only correct answer you can give is some variation of either "Protestants believe the Catholic Church is wrong", or "Protestants believe the Catholic Church is not the only true Church". Everything else will conform to one or more of the following statements:
1. The Catholic Church will actually agree, e.g. "Protestants believe in the Trinity". You would call me a Protestant, yet because the Trinity is taught in scripture, I believe the Trinity, just as the Catholic Church does.
2. It will not cover all Protestants, e.g. "Protestants believe in Sola Scriptura". I've actually been mocked by someone you would consider Protestant because I used the doctrine of Sola Scriptura to refute his position that some Christian songs are from Satan because the tune is "wrong".
3. It will cover a belief that genuinely is a new belief, yet once again, it will not cover all Protestants. e.g. "Protestants believe in Calvinism". Personally, I'm a "Mediate", neither Calvinist nor Arminian.
You see, then, that the term "Protestant" makes about as much sense as the term "atheism". And there genuinely is a push for that. Stephen Roberts, for example, says "I contend we are both atheists, I just believe in one fewer god than you do." Am I an atheist because I don't believe in Allah? No. I reject Allah because I believe the Bible. So am I a Protestant because I don't accept the Catholic Church? No, I reject the Catholic Church because I believe the Bible.
As a Christian, there are certain beliefs I hold that the Catholic Church opposes. I held most of these beliefs before I knew what Catholicism taught. There are no beliefs I hold just because I reject the Catholic Church. As a matter of fact, there are no beliefs I publicly profess that I cannot defend exclusively from the scriptures. Therefore, any attempt to describe me as a "Protestant" is just a feeble attempt to implicitly gain significance. It has the hidden implication that Catholicism came first, and the beliefs I hold exist only to protest them. In truth, it is the Catholic Church, which so frequently opposes scripture, even to the point of scoffing at the doctrine of Sola Scriptura, that came later. As a Christian, I don't protest the Catholic Church, but the Catholic Church frequently protests God. Therefore, Catholicism is the true Protestantism, and Catholics must repent.