Yes, Virginia, "intelligent design" is creationism
If agreement as to the empirical vacuity of "intelligent design" among the scientific and skeptical communities runs at about 99%, then consensus as to classification of ID as a subset of creationism runs close to that. But it is something that is occasionally argued. Not all critics of ID agree that it can be legitimately referred to as ID creationism.
Obviously I am not one of those exception-takers. I think it is important to make it clear why.
I see this designation as a question of scale and context. While it is important, and logically necessary in certain circumstances, to be able to appreciate the distinctions between ID and YEC, discussion of the larger picture requires us to give much more weight to the similarities.
I suspect that for virtually all creationists it is their beliefs that define who they are, and it is in the context of these beliefs that they are able to judge themselves as upright and straightforward. But all who oppose them have experienced the frustration of creationist actions that appear to directly contradict their belief system. We wonder how this kind of self-deception is possible.
For me, and I suspect it holds for others as well, this is because I consider the material aspect of the creationist interaction with society to be their behavior, their activism, not their beliefs. Most of us could care less about the guy who goes to church every week and believes that God created in 6 literal days 6000 years ago, but keeps his nose out of science and his hands off of education.
I would suggest, then, that the common usage of, perhaps even an accurate definition of, “creationist” must rely as much on socialization as it does a particular set of beliefs. No one, but for a few religious apologists and militant atheists, would think twice about creationists if they stayed at home or in church and ignored politics and science. "Creationism" as a label encompasses activist evangelism, and that invariably begets political activism.
As such, I place much more importance on the goals, strategies, and alliances of any particular variant of creationism than I do on the arguments it employs. No, ID "theory" does not advance the exact collection of arguments that traditional creationism does, but it has the same ultimate aims, uses the same tactics, and makes common cause with traditional creationists.
In addition, advocates of ID and creationists tend to employ similar arguments during debate. They both spend most of their time finding fault with evolutionary biology, as if this supports an inference to a "designer." They both make faith statements, though ID proponents attempt to disguise these with "impossibility" assertions and probability calculations. And while ID proponents emphasize that they do not claim God poofed individual species into existence is there any real operational difference between this assertion and one that God poofed into existence flagella and other biomolecular structures? No there isn't, they both invoke fiat creation.
When viewed within the framework of historical precedent the term "creationism" must, in my opinion, be more broadly understood and applied than as a simple designation for a specific set of scripture-based assertions. Creationism has a long and unambiguous socio-political resume. And a brief survey of "intelligent design's" resume indicates it has been creationism from its very inception.
Of course this observation doesn’t sit well with ID proponents. “Scientific creationists” thought they brought more to the table than their bible-thumping predecessors, and likewise ID types certainly have felt all along that they deserved more credit than their forebears. They don’t appreciate being lumped with “creationists” of any kind. There are at least two reasons for this. The first is obvious, it immediately marginalizes their movement to have it linked with previously failed ideas. In addition, I suspect there are those in each species of creationism who truly believe they’ve gone beyond superstition and have found the key to uniting science and religion.
Thus I think it is both good analysis and good strategy to continue hanging the creationist label on ID proponents. I agree that there are times when understanding the differences can make or break an argument. And I also agree that it can’t hurt to highlight those differences that may lead to significant breaches in the big tent. But I think these are considerations of narrow context when compared to the overarching thrust of creationism.
None of this means that I don’t recognize the different species of creationism, nor do I discount their validity. But I believe the reality is that, absent the political activism, “creationism” (of all types) is interesting only to a very limited community. That community would have neither the will nor the ability to press the kind of destructive changes to science and education sought for so long by creationists. The term might never even have acheived its current ubiquity.
But of course creationism does bring with it the militant evangelical behavior (disguised, as with ID, or not), and so it becomes interesting to a great many of us. As such the distinctions that define creationism variants shrink drastically in importance.
"Intelligent design" is indeed one of those variants, but it is creationism nonetheless.