There are two things I find particularly annoying about modern religious discussions. The first is that people treat written texts as ink blot tests. The former is designed with the intent of being interpreted, and there are fewer valid interpretations than invalid. By contrast, an ink blot test is genuinely open to a wide variety of interpretations. Few interpretations are invalid, if any at all.
The second is that people treat the mere existence of an opinion as validation thereof. Thus, they argue, it is somehow wrong to discredit this opinion, or to have particular confidence in your own. Conveniently, this only ever works one way. Those same opinions are not evidence that the one highlighting them ought to be less confident in their own view.
With the Bible, both of these fallacies are often merged. Implausible interpretations are defended by either their own existence, or the existence of other implausible interpretations, and the clearest interpretations are attacked on the sole basis that there are those who do not hold them.
The most recent example in my personal life is an atheistic Evolutionist I debated on the topic of whether or not Evolution is linked to atheism. Initially, it wasn't even him I was discussing with. He just inserted himself into the conversation to dispute two quotes I had cited by atheists. The two quotes are:
"...Darwin made it possible to be an intellectually fulfilled atheist." (1) - Richard Dawkins
"One can have a religious view that is compatible with evolution only if the religious view is indistinguishable from atheism." (2) - William Provine
The Evolutionist, without any reason what so ever, disagreed with the quotes, asserting his position that atheism and Evolution are linked in no way, shape, or form. I began to show him otherwise, and after a few really silly arguments, he eventually pointed out that there are many Christians who believe in Evolution. To this, I simply said they're hypocrites, because "the Bible is quite clear on the topic of origins". His response, rather than to actually give evidence to the contrary, was to ask "If it's so clear, why do so many Christians disagree with you? I have Christian friends who believe the creation story is a metaphor."
At the time, my simple response was if it isn't so clear, why is it there were no such disputes until atheists started putting a scientific veneer on Evolution? The book of Genesis is pushing 3,400 years old. Even before we reach the New Testament, a collection of firmly Creationist books that ground a lot of their own doctrines in a historical interpretation of Genesis, you will never find anyone who interpreted Genesis as a metaphor.
The interpretation wouldn't even make sense. A metaphor for what? This is one of many questions you can ask someone who holds to a compromised view of Genesis. Unlike Creationists, Theistic Evolutionists and the like do not have a well developed theology. Their beliefs primarily center around a denial of particular interpretations, not on any kind of desire to draw applicable meaning from the text. Thus, when they default to "it's a metaphor", that's typically where it ends. They have no further explanation for what it means, nor do they have responses to arguments against this interpretation.
Ironically, if we limit our sample to only those who are in a position to know, the number of dissenting voices drops significantly. As an example, Hebrew scholar James Barr once wrote a letter to David C. C. Watson, in which he wrote "...so far as I know, there is no professor of Hebrew or Old Testament at any world-class university who does not believe that the writer(s) of Genesis 1–11 intended to convey to their readers the ideas that:
a. creation took place in a series of six days which were the same as the days of 24 hours we now experience
b. the figures contained in the Genesis genealogies provided by simple addition a chronology from the beginning of the world up to later stages in the biblical story
c. Noah’s flood was understood to be world-wide and extinguish all human and animal life except for those in the ark.’" (3).
The question can therefore be flipped on its head. Rather than "if Scripture is so clear, why do so many Christians disagree", we can ask if Scripture is not so clear, then why do so many knowledgeable Hebrew Scholars agree with me?
But both arguments are almost equally dumb. My version would be slightly stronger. If the overwhelming majority of experts all come to the same conclusion, we can surmise there must at least be some reason for that. It would still be a fallacious argument, but it's still weightier than "my Christian friends have a different interpretation."
But at the end of the day, the correct position isn't the one with the highest popularity. Truth and Democracy never did work well together. As I pointed out in the same debate (because of course the Evolutionist had to appeal to consensus to make his case), consensus actually hinders the pursuit of truth, such as when Galileo made a stand against the geocentric model of his era. In fact, there was a time when "young" Earth Creationism was not only the unanimous opinion in the Church, but also in science!
But it's all well and good pointing all of that out, we still haven't answered the question. If Scripture is so clear, why do so many Christians disagree? As I've already said, the existence of an interpretation does not validate it, but what you'll find is that those who hold such invalid interpretations struggle to validate it themselves.
In the case of Creationism, it's so clear in Scripture that dissenting voices all echo the same sentiment: "Genesis isn't supposed to be taken literally". What is this a confession of? It's a confession of what Genesis literally says. The creation account is so perspicuous that the only way to dispute it is to confess it first. What that means is there is actually an onus on those who doubt the interpretation to show that this doubt is plausible.
What they could do, if indeed they were correct, is do so using ordinary means. If, for example, I wanted to prove that the parable of the sower is a parable, I could point you to Matthew 13:3, which says "Then He spoke many things to them in parables, saying:...", and then leading off into the parable. We can even surmise that actually, a lot of what Jesus said is figurative, because the disciples were amazed when He didn't use figures of speech (John 16:29). So we don't need to take Jesus literally 100% of the time. He used many things from explicit parables, right the way to obvious metaphors. We're talking about a God who describes Himself as a vine, a door, and even bread, none of which are literal, and none of which give us reason to believe otherwise.
But when it comes to the Genesis account of origins, the opposite is the case. There is, of course, some figurative language. The moon is not literally a "great light", for example. But how many people wonder if NASA still hold to the geocentric model when they talk about sunrises and sunsets? But overall, the entire rest of the Bible treats Genesis 1 - 11 as literally as it treats Genesis 12 - 50.
The long and short of this is that if you want to know why people disagree with the clear interpretation of Genesis, you shouldn't ask someone who follows it, you should ask someone who disagrees. Their disagreement has no bearing on the truth.
What it does do, however, is show a lack of confidence that you have it. See, those who are confident in their view defend it on its own merits. Christians even have a saying that you don't need to defend the Bible any more than you need to defend a lion. Just let it out of its cage and it'll defend itself. But the strategy for unbelievers seems to be to distract entirely from the topic at hand by discussing the views of people who aren't even involved in the current conversation.
Of course, while the example I have chosen a specific example in this article, we live in a world of endless rhetorical incompetence, wherein this kind of abysmal logic is spread far and wide. You can pick any issue, it is guaranteed someone will argue their case by pointing to someone else's. Atheists point to Muslims when trying to shut down Theism. Roman Catholics try to dispute Perspicuity by asking about Mormonism. Muslims ask how we can be confident in the Deity of Christ when Gnostics certainly didn't hold such views. It's unfortunate, but we have a bottomless supply of people who are so afraid to defend their own views that they will effectively ask their enemies to do it for them. It is my hope and prayer that one day, education standards will rise to a level where such folly is eradicated. For now, I hope I have at least exposed it to my small audience.
References
1. Dawkins, Richard - The Blind Watchmaker, 1986
2. Provine, William - “No free will” in Catching up with the Vision, Margaret W. Rossiter (Ed.), Chicago University Press, 1999
3. James Barr, Oriel Professor of the interpretation of the Holy Scripture, Oxford University, England, in a letter to David C.C. Watson, 23 April 1984