Why do "evolutionists" and "creationists" insist on being so diametrically opposed to each other, to the extent that they consider each other mutually exclusive? The Bible does not contain specifics about many things, including the processes of evolution and creation simply because they are not important to the story of God's relationship with man. In fact, there is sufficient evidence to support the validity of both perspectives. Why couldn't God have created the world very much the way the scientific evidence suggests?
I, of course, can’t answer for all creationists or evolutionists as to why they do or think anything. I can only answer for myself as a creationist. I do have some ideas that may explain why some disagree so vehemently with the others.
Most of us who are “creationists” believe in evolution. Evolution is a proven fact. Yet evolution, in another sense, is an unproven and unprovable theory. That is, what is called microevolution (evolution within species) is an established fact. People are different today than they were years ago. The Labrador Retriever, as a breed of dog, is only about a hundred years old. Darwins finches are different than other finches. But macroevolution (the theory that all creatures are descended through distinct lines from a singular beginning with no divine initiation) can no more be proved than the theory that God created everything in seven days.
That said, I believe that the Bible is true and consistent. Therefore, I must believe that macroevolution is wrong because of its insistence on vast time periods to develop the various classifications of life. If God created in seven days of twenty-four hours each, that necessarily means that man and the dinosaurs came about within days of fish and birds. Of course, there are some who want to believe that God created the initial cells and let evolution run its course, but that requires them to mythologize the Bible.
Many evolutionists accept a theory of evolution that denies God had anything to do with creation, just because they refuse to believe in God. They want a materialistic explanation for the development of life on earth, even if that explanation is full of holes. Those people would then be adamant that their theory must be true and that God could have nothing to do with it, because they want to refuse to believe in God.
The Bible states that birds, fish, whales, cattle, “creeping things,” beasts of the earth, and man were all separate and distinct creations. (Genesis 1) If one accepts that the genealogies of the Bible leave out generations (therefore increasing the time for microevolution), then it is possible for a creationist to accept a limited theory of evolution. God created a small number of “kinds” of animal or plant, and the many variations within those kinds have developed over the years. This would even explain how Noah could fit all those kinds of animals in the ark (two dogs, for instance, rather than two collies and two setters and two shepherds). Most evolutionists won’t accept this brand of evolution, however.
Others, yet, will say that evolution and creation are two separate ideas that have nothing to do with each other. Evolution, for the most part, does not claim to explain the origin of the building blocks of the first organisms. It just argues for the development after those building blocks were created. Creationism, as you point out, generally does not argue the mechanism after the creation. So in a sense they are two different disciplines that need not disagree.
Why couldn’t God have created the world the way the scientific evidence suggests? That depends on what you think the evidence suggests. There are those who argue that the fossil record actually suggests the limited evolution suggested in the previous paragraph. Since the fossil record shows no development of higher forms of life prior to the “Cambrian Explosion” (the sudden appearance of a variety of fully formed new kinds of life during the Cambrian period) many will say the evidence suggests that God created different kinds and let evolution take its course thereafter.
Basically the answer to your question about why the two “sides” are so opposed to each other is that each theory is based on a specific faith. One is a faith in God. The other is a faith that God does not exist. As with most faiths, the proponents of each believe that theirs is the only true faith and accept the evidence that supports their belief system. And, as with most faiths, neither faith can be proved to the satisfaction of those who don’t want to believe.