Interesting Ian said:
I personally have no problem with acausal events whatsoever.
Most people do; it's one of the big stumbling blocks behind the acceptance of Quantum Theory (first by scientists -- Bohr: "Einstein, don't tell God what to do!", and later by the general public). But the issue of causation, the problem of acausal events, and the ultimate association of "God" with "the only acausal thing" goes way, way, back before that --- I believe that Aquinas is the person usually credited with formalizing the "God as prime cause" argument for the existence and nature of God.
I also don't think that anyone claimed that ID proponents "must" use the argument you straw-manned (is that a word?). On the other hand, they demonstrably
do, in part because it's very superficially compelling in part
because most people have issues with acausal events. (See Aquinas above).
One thing that may help is to rephrase the nature of ID proponents. Among their many other fallacies is buried a false dichotomy --- either Christian-style creation
ex nihilo is true (typically on a time-scale associated with young-Earth Creationism), or else evolution is true. So they cast their task not in terms of "proving ID," but of "disproving evolution." By the law of the excluded middle, if evolution were to be proven impossible, then YEC would thus be correct. (As I said earlier, I don't think anyone on either side of the issue takes seriously the idea of space aliens doing genetic tinkering with proto-apes, or with the idea that Gaea and Ouranos created the world by giving birth to the Titans, etc.) The issue of acausation is simply one among many arguments that they raise against evolution.