Creationists reject Darwin's theory of evolution on the grounds that it is "just a theory". This is a valid criticism: evolution is indeed merely "a theory", albeit one with ten billion times more credence than the theory of creationism - although, to be fair, the theory of creationism is more than just a theory. It's also a fairy story. And children love fairy stories, which is presumably why so many creationists are keen to have their whimsical gibberish taught in schools.
oh charlie, how you rock.