Scientific creationists are part of a movement that seeks to establish through government policies a particular religious doctrine contrary to the principles of the United States Constitution. The movement is strongly authoritarian, patriarchal, militaristic, and opposed to public support of social welfare programs. This New Religious-Political Right represents not just a disagreement about scientific interpretations but a serious effort to buttress the economic and political power of the traditional American bourgeoisie. The debate over evolution versus creation is at once a side effect of the movement's world view of antitheses and a means of identifying those who will follow authority in the movement. To put one's signature to a declaration that one accepts on faith the "absolute inerrancy of the Bible" is public witness of one's willing submission to authority. Nothing scientists outside the movement can say can change the minds of those who have declared their a priori commitment to "Biblical revelations (as) absolutely authoritative." Scientists who feel compelled to challenge the movement must look to the political arena.That's really all there is to it. There's nothing terribly bad about evolution per se from a theological perspective. Religious theodicy has subsumed plagues, earthquakes, the Inquisition, the Holocaust, the genocide of the Armenians and American Indians, cancer of the rectum and jock itch; theology can handle evolution without too much trouble.
Alice B. Kehoe, Scientific Creationism: World View, not Science (1987)
A large number of religions are authoritarian, to a greater or lesser degree, with priests and prophets acting as proxies for the ultimate authority, God. All authorities require a shibboleth, and the most tyrannical of authorities require some proof of submission, proof that his supposed authority is not vacuous, like that of the Little Prince's King, who commands the stars to do what they would do anyway.
Evolution is a perfect candidate not because it poses any theological difficulty but precisely because it is so well established. A reasonable, educated person not in thrall to a religious authority cannot rationally deny the scientific validity of evolution. Therefore, an authoritarian submissive denies evolution to prove his submission overrides his rationality and education.
Heliocentrism, quantum mechanics, General Relativity, any of these ideas could suffice almost as easily; evolution happened to be the controversial idea facially at odds with religious dogma at the time of the American religious revival in the early 20th century.
Evolution denial has very little to do with either science or theology. It's all about the authority.