One man's theology is another man's belly laugh.Robert A. Heinlein, Time Enough for Love, 1973
I suppose Heinlein's nutty ideas in Stranger in a Strange Land would the best proof of his statement-- maybe as a fan of his you would know how much (if any) of that book was meant seriously rather than as satire.
Incidentally, it seems to me the premise of this thread fails the smell test for intellectual fairness. If someone made the criticism that liberalism (defined as the term is commonly used)equals Communism after listing the evils of Communism, I'd say that he was poisoning the well. A similar line of reasoning is often used by leftists--- list the errors of Shockley regarding race, declare that Murray and Hernstein are equivalent to Shockley; then, after poisoning the well, go on to make criticisms of Hernstein and Murray.
Of course, many Creationists are proponents of some form of Intelligent Design. Many atheists are Darwinians; that doesn't make Darwinism the same thing as atheism anymore than the fact that many Darwinians are Christians means that Christianity is a form of Darwinism or vice versa.
The only assumption that ID posits is that it's possible to make design inferences based on the specified complexity one finds. That's all there is to it. Creationism, as I understand it, is in its broadest sense the notion that God created the universe, more specifically that God in one way or another is responsible for life on Earth, and in Young Earth Creationism, that the sort of literal interpretation of the Bible that became popular among Seventh Day Adventists and spread from there, that the Earth is only six thousand or so years old and was created in seven 24 hour days. The differences are clear. A Creationist need not buy into the notion of design inferences at all--- he can simply say, "I take the Bible to be saying x and therefore x must be is the case and all science must be done within the constraint that x is the case". For his part, an IDer need not have any faith in the Bible to be an IDer-- certainly Aristotle and Voltaire, who each promoted different forms of the design argument, did not. So ID forms no necessary part of Creationism and no aspect of Creationism forms a necessary part of ID.
One may fairly present reasons why either ID or creationism or both are silly and stupid. One may claim that were Voltaire or Aristotle were alive today, they would recognize the error of their ways, or that the Bible does support the interpretation Creationists place upon it. But to conflate them is to either make a category mistake or to be purposefully sloppy-- to take a short cut when reasoned argument is determined to be too much trouble.