It should surprise no one that conservatives would have little interest in evolution. After all conservatism is at its core a philosophy that thinks change is bad. Evolution, with its message of adapt or die, runs directly counter to the aspirations of conservatism, and that's before one considers any theological impact caused by an acceptance of evolution.
By that logic one can just as easily say it should surprise no one that progressives would have little interest in thermodynamics. After all progressivism is at its core a philosophy that thinks change is good. Thermodynamics tells us "social progress" is actually just a progression toward the entropic heat death of the universe guaranteeing the destruction of all life and worldly pleasure.
I don't think very many people actually think that way. The reason why some conservatives don't believe in evolution is for theological reasons not an because they see it as saying they need to change or die. It challenges many characteristic tenants of American Christianity and its views on Biblical literalism and Biblical historicity that many Christians don't feel comfortable with having challenged.
The reason why a lot of Americans don't believe in evolution isn't because people have banned it from being taught or neutered its message in schools. That is an effect and not a cause. The reason is that American culture contains a narrative of a false dichotomy between faith and science where the two must be seen as opposed. Public schools are not permitted to discuss such topics with much latitude for a variety of reasons, some justifiably, but absent a discussion involving faith, reason, what science is, what it tells us, and what it can't, there are a lot of people who will simply reject evolution as a "theory" (despite seemingly no one having the faintest clue what that means). Thus we continue to circle the wagons and will do so for some time. Bludgeoning people with outrage will convince no one however; that would require explaining it to them in earnest in ways they have never considered. It probably needs to be the right person to do the convincing too. St. Augustine may work better than Richard Dawkins.
On its importance, the fact that evolution is a litmus test in and of itself is a disservice to science as many of those who reject it might have made good chemists or computer programmers or something of the like had they a greater appreciation for science as a whole. It clearly is critical to understanding most parts of biology and it's tough to see many people who disbelieve in evolution entirely as successful biologists or most kinds of doctors. In my opinion though, if I were to lament about one thing in the STEM area hampering our technological and economic development, it would be the number of high schoolers who are not proficient in calculus.
