The answer should be obvious. Scientists (and philosophers of science) set the rules for what is science. This is as it should be. Consider if someone presented a text in Hebrew and claimed it as a previously unknown book of the Bible, who would decide if this claim is true? Who would decide if it were really the Word of God or not? Certainly not scientists, but rather clergymen and theologians. Defining science should be done by people who study it. The difference between accepting intellegence in things like SETI and in biology is that in the biology case, by accepting intelligence you are assuming the very phenomenon you are trying to explain. You are saying that intelligent human beings exist because of the design of some other intelligent being. This then begs the question of where did the other intelligent being come from. You either get an ad infinitum regression, ie. some other intelligent being number 3 designed intelligent being number 2, and intelligent being number 4 designed number 3, etc., or you arrive at God. The first case is absurd and the second is not science. Science, by definition of its methods, seeks testable physical explanations for physical phenomena. God certainly is not a testable, physical explanation. Indeed, that's what faith is all about, believing in God despite the fact that there's no physical evidence for such a belief. I am NOT arguing that intelligent design cannot possibly be true. Not all truth comes from science. I am simply arguing that ID does not belong in a science journal (or a science classroom for that matter).
Maybe one for the ping list???
Very well said, basically said verbatim my personal position on the subject, though I could never write it that well.