Allies of ID creationism have filed a friend-of-the-court brief in the Kitzmiller case which you can read here. It essentially argues that the court should not address the scientific validity or invalidity of ID; "[T]he scientific theory of intelligent design [sic] should not be stigmatized by the courts as less scientific than competing theories," the brief argues. (p. 5) Of course, determining that a set of assertions is not scientific is not necessarily to "stigmatize" those assertions, but simply to understand their nature; it's not stigmatizing a duck to say that if it quacks and waddles and has feathers, it's a duck. ID is not science because it is not a testable explanation of natural phenomena in terms of other natural phenomena. Instead, it's an assertion that phenomena can only be explained by invoking non-rational, non-testable, non-repeatable magical phenomena.
Nevertheless, the amici claim that ID is a "theory based upon a scientific evaluation of the empirical evidence." (p. 6). Where are the testable theories? Where are the explanations of phenomena in terms other than a juvenile assertion that "Such-and-So is just so complicated that it must have been designed"? Well, the brief admits there are none: "the current formulation of intelligent design theory," it says, "is still in its youth.... For that very reason it is premature to conclude that one side has triumphed and the other has lost." (pp. 6-7) Premature? It is senseless to wait for ID to "triumph": it is an interpretation based on untestable, supernatural phenomena. ID proponents may dress up their claims with sophisticated names, but they truly consist of nothing more sophisticated than the assertion that things are just too complicated to have come about through natural processes.
This assertion cannot bear scientific fruit, no matter how much time is given it. It's noteworthy, for example, that the brief cites not a single scientific paper; nor does it attempt to describe any theoretical insights of ID. Instead, it admits, as it must, that ID consists of nothing but an emotionalistic appeal to a general feeling that something must have been designed: "Even critics of design concede that the possible conclusion of design influences their thinking," the amici contend. It quotes Francis Crick, Richard Dawkins, and Bruce Alberts; Alberts, for example, "has acknowledged that cells resemble human-designed machines." (p. 10). Sure---as have we all. But the difference between science and nonsense is that science explains that this resemblance is due to a natural mechanism of selection between random variables; it does not appeal to the whim of some ineffable Mind that has chosen that it Shall Be This Way. Nonsense looks at an array of data and concludes that it must have been intended to be that way---an answer which provides nothing useful, and which is entirely arbitrary, since it could equally "explain" any set of data.
The brief makes no scientific argument at all, and gives no indication of where the court might look to find a scientific argument. Instead, the amici contend that the scientific community ought to welcome debate. "The scientific enterprise advances when scientists make new discoveries correcting or overturning previously held theories." (p. 7). Well there's no denying that, and certainly nobody would be more pleasantly delighted than I, if proponents of ID were ever able to come up with a new discovery. But the classrooms of government-operated elementary and high schools are simply not the place to make new discoveries! The place to make new discoveries is in the laboratory, in the field, and in the pages of peer-reviewed scientific journals, in none of which have the proponents of ID produced a single workable idea. If it is "premature" to expect ID proponents to produce the evidence with which to "advance" the scientific enterprise, then it is way too premature to allow ID proponents into the classroom. ID proponents seem to be asking for a "general warrant": let us into the classroom first, and we'll give you the evidence to justify our admission later! And if you point out that they're skipping a step, then you're "stigmatizing" them.
For a second, let's apply this analysis to a hypothetical: let's say Matt Hale of the World Church of the Creator wants to teach children in a government-run school that God made white people smarter than black people and Jews. Don't you go calling him an anti-Semite, now, because that's just an "ad hominem attack." (Cf. p. 12). And don't go demanding that he prove his claims before teaching it to children---he'll get to that later, you know? For now, it's important to teach children to keep an open mind about all sorts of different ideas. After all, Hale could be the bellwether of a new scientific paradigm!
Fortunately for us all, the First Amendment stands in the way of at least some of these attempts to co-opt the schools for the benefit of particular interest groups. It forbids government from teaching religion. Reference to a Supernatural Designer as the origin of species is religion; it does not belong in the classroom---a point which the authors of the brief nowhere discuss. Instead, they characterize it as "bigoted" (p. 12) to point out that these proponents are motivated by a desire to teach children the existence of a Diety in taxpayer-supported classrooms. And attempts to keep religion out of the classroom? Why that's nothing but the goal of a bunch of atheist scientists trying to corrupt our youth: Eugenie Scott is a Humanist (p. 15), Steven Weinberg (correctly) describes religion as superstition (p. 16); Barbara Forrest is a member of a secular humanist society (p. 16), and 95 percent of the biologists in the National Academy of Sciences are atheists or agnostics (p. 17). "Amici detail these affiliations not because religious (or anti-religious) beliefs are relevant to scientific argument,"---oh, of course not!---"but to demonstrate that the legal rule proposed by the plaintiffs would jeopardize the scientific contributions of many critics of intelligent design." (p. 18). What is the "legal rule" proposed by the plaintiffs? Why, nothing but that allowing a group of people who openly admit or badly disguise their religious intention to get into a classroom and teach children that science doesn't explain things, but that a Supernatural Divine Creator of All is instead an equally valid hypothesis---now with State Approval!---is unconstitutional.
This remarkably similar to a rhetorical device we've been hearing more and more recently from religious conservatives: that any attempt to keep the government out of the religion business is somehow to positively violate the freedom of religion. In their eyes, religious liberty includes the "right" to use taxpayer money to propagate their religious views, and to use the state's authority to put a seal of approval on their religious beliefs. And when someone denies them the opportunity to use the state in this way, they cry that their freedom is being violated. Well, I'm sorry, but that isn't how religious freedom works. Freedom means, you stay on your side and I'll stay on mine, and you can do what you want in your yard and I can do what I want in mine. It doesn't mean your freedom to take my things and put the state's Seal of Approval on your religious beliefs. The rhetorical trick of painting enforcement of the Establishment Clause as somehow actual persecution of religious freedom is deeply misleading and, if it works, quite dangerous.
I will say this for the AC brief: it is a masterpiece of ID thinking. It brilliantly encapsulates the entire ID movement: skip over the problem of providing a theory or evidence, call your opponents names like "bigoted" while simultaneously playing the victim of an international conspiracy of atheists; rely on non-scientific books and press releases, and appeal to the supposed "fairness" of teaching "competing" theories---no matter how baseless. And all along, insist that ID is "science," despite its inherent appeals to supernatural, inexplicable, unrepeatable, useless notions of the Will of a Divine Creator: a Creator to Whom we never, ever characterize more thorougly, or name explicitly.