Not because it’s false, mind you. There is no reasonable definition of science that includes Intelligent Design and Creationism, and it is perfectly legitimate to point that out. In certain contexts, like when you are arguing that it is unconstitutional to teach ID in public high school science classes, it is even an important and relevant point.
But it is not the main reason serious scientists want nothing to do with the notion and it should not be the first thing you say when debating the subject. Case in point, consider how the usually excellent Steven Novella opens this post about ID:
The primary scientific criticism of ID is that it is not a legitimate scientific theory, but rather a transparent attempt at recasting religious faith (creationism) in scientific-sounding jargon.
No, no, no!! That is not the primary scientific criticism of ID. The primary scientific criticism of ID is that the specific assertions made by ID folks, about irreducible complexity, complex specified information, the alleged holes in evolutionary science, and so on, are universally false. That’s why scientists reject ID.
Stating things as Novella has plays right into ID hands. It creates the false impression that scientists won’t give ID a fair hearing because it fails to conform to some definitional contrivance. The reality is much simpler and so much more powerful. ID’s scientific claims are rejected because they are wrong, in precisely the same sense that it is wrong to say that 1+1=3. ID claims are wrong independent of whether evolution in its modern form is substantially correct. If tomorrow a stunning discovery is made that shows common descent to be a lot of nonsense, it will still be true that William Dembski’s probability calculations are meaningless. It will still be true that his use of the No Free Lunch theorems is not legitimate. It will still be true that “irreducibly complex” biological systems can evolve via a variety of well-understood mechanisms.
Just so we are clear, ID isn’t science, and it is just a transparent attempt to conceal an especially blinkered sort of religious faith beneath the clothing of science. That, however, is not the primary reason that scientists reject ID. Nor should it be. If there were any merit to the charges the ID folks make, their lack of conformity to some definition of science would hardly be the big news.
That said, go read the rest of Prof. Novella’s essay. After my annoyance at his opening died down, I found I enjoyed it a quite a bit.