Correction: there's no rational reason for it.
Ironically, however, there is a common assumption on both sides of the shouting match: that "evolution" and God are mutually exclusive.
The militant anti-evos are (perhaps) so insecure in their belief in God that they're afraid the theory of evolution endangers God.
The atheist pro-evos are so insecure in their disbelief, that they latch onto anything that seems to bolster their case.
Within that context the anti-evolution position is most difficult to defend, as there is strong evidence supporting the presence of at least some of the processes associated with the Theory of Evolution. Their tacit acceptance of the claims of the scientific method leads anti-evos either into a "God of the Gaps" position, or one of outright rejection of the scientific observations.
On the other side, it's interesting to watch the process whereby any non-evolution theory is a priori rejected as "non-scientific." Thus, the idea of an intelligent designer is rejected outright. Not for any good scientific reason, but rather because the admission that ID is a valid hypothesis admits at least the possibility of God. (Note that genetic engineering is proof that ID can be a valid hypothesis. Verification of a particuar hypothesis is, of course, a separate matter.)
That was worded carefully. My contention is that I would like to see a clear distinction between what can be scientifically observed and what is extrapolated based on those observations. Teach the theories, but also teach the limits of what is truly known.