Those who do insist on a literal reading are inevitably inconsistent about it. For example, when confronted with the scriptural description of pi as 3, or of the earth being immovable while the sun circles around it, the most imaginative contortions are employed to explain that scripture doesn't really say what it literally says. The same is true of some other passages that show up in these threads from time to time. Yet these interpretive skills are never applied to the creation account in Genesis -- which many denominations read as an allegory -- and which must be an allegory, considering all that we've learned about astronomy, geology, etc.
Why do literalists behave like this? Why draw the line at Genesis, and not at pi, or geocentrism? Because -- this is my opinion only -- some people literally enjoy such controversy, but even the Kathy Martins of the world dimly sense that it's clearly insane to insist that the "controversy" about pi should be in the schools. So they draw their battle lines at Genesis, poor ol' Darwin becomes their villain, and children are being systematically confused about how to think about reality.
We can all agree that there are some passages that are only poetry, or allegory -- and they usually signal quite plainly that such is what they are. But there are other passages (pi and geocrentricism) where we are left clueless by the text alone.
That's where science comes in. Science is an investigation of nature -- or of creation -- God's first book. The universe is in God's original handwriting. Un-transcribed, un-translated, un-edited. It's the primary source, the real deal. It's the context in which scripture should be understood, and not vice versa.
You make some excellent points here.
Much (most?) of the 'heat' in the arguments from the Creationist side seem to me to arise from basic misunderstanding of the scope, methodology and findings of ToE. These points are best addressed by patient reiteration of the sources
Some of the 'heat' comes from fear--and for that, I have much sympathy. Much that we all hold most valuable--family values, personal freedom, democratic government--has indeed been under ferocious assault by liberal ideology, with disasterous consequences. Much of this assault comes from the school of Marxist dialectical materialism, which I think becomes conflated in some people's minds with scientific empirical materialism. But of course there is no actual commonality: Marxism starts from a ideological stance which it falsely attempted to dress up with the trappings of science (in a manner very similar to the pseudo-scientific packaging of Intelligent Design), whereas science is exclusively concerned with examination of Nature--the material world.
Arguments from analogy are hazardous, I know, but they are beloved by some in the ID camp. So here is one:
The philosopher Ludwig Wittgenstein (for whom I hold no brief, btw) once declared something along the lines of, "I simply do not understand why people once thought that the sun circled the earth." A colleague at once answered him, "But Ludwig, that is not surprising at all--after all, that is what it looks like!" But Wittgenstein professed to remain baffled. "It does? But, would would it look like if a spinning earth was orbiting the sun?"
His point, of course, is that it looks precisely the same. To me, when someone says that "But just look at something complex like the eye--how could that arise except by the hand of God/Allah/Flying Spaghetti Monster (delete as applicable)?" one really must answer, "But what does it look like according to the mountains of evidence for evolution?" Precisely the same. It's just that one model is correct, and one is demonstrably false.