Overwhelming hard data from biology, geology and anthropology — gathered with a firm grasp of the workings of evolution — prove false the claims made by creationists.
Earth is not 6,000 years old and it wasn't shaped by a great flood 4,500 years ago. (Earth is 4.5 billion years old.) Humans and dinosaurs did not coexist. (These life forms missed each other by many millions of years.)
When creationist claims are put forth as science in museums or taught as science in schools, our children lose out because their science literacy is diminished.