Even its critics must grudgingly admit that intelligent design has succeeded brilliantly in marketing abstract concepts by courting the media and general public. But ask those critics whether it is good science and many will go cross-eyed and begin frothing at the mouth. What is it about ID that brings out the worst in some people? Alas, the reasons are many, including the long and tortured history of creationism and the courts. (Read Langdon Gilkey's Creationism on Trial for a sampling as well as Ron Numbers, The Creationists.)
But a history of failed attempts to get equal time for creationism in the classroom, as well as more recent attempts to do something similar for ID, are no excuse for bad arguments. It is most unfortunate then that many scientists, those who are supposed to be paragons of rational thinking, often resort to school yard insults when it comes to ID (one of the most memorable, and idiotic, being "intelligent design is creationism in a cheap tuxedo").
Push beyond that penumbrial belt of sophmoric name-calling and you come next to the really bad arguments of which there are sadly many. Here is my candidate for the very worst: "Intelligent design is not science because it doesn't provide any new information. It is purely negative." According to this objection, legitimate scientific theories are identified by being explanatorily productive and predictive, and ID is neither.
In my view, IDs leading theorists have amply rebutted the charge by showing that ID is both productive and predictive (the true nature of "junk DNA" being a prime example). But even if we were to concede that ID did not provide new insights into nature, the charge would still be wholly spurious.
Why, you ask? Well consider a detective attempting to discern who murdered a little girl. The predominant theory says that the step-father did it. Let's say that the detective identifies evidence that eliminates the step-father as a suspect. Would that be worthwhile information? Of course! It would be invaluable, both for exonerating the step-father and at the same time eliminating a dead end of enquiry. Try to imagine the detective's superiors telling him: "This information is useless! Come back when you know who did it!"
The parallel with ID should be obvious. Even if ID theory tells us nothing more about the natural world than that certain biological structures could not plausibly have emerged through random mutation and natural selection alone, that is still an invaluable piece of information. There may be points where ID is in need of critique, but this is surely not one of them.