People claim that god interferes with mankind and causes things to defy known laws of physics. These things can be tested. Otherwise you are correct, someone that merely has faith, has no reason to prove to me or anyone else. However, as soon as someone makes a positive claim about said deity, as is claimed by creationists, we have something to go on as they are presenting evidence for the existence of their god. Is it not reasonable to reject such claims and insist that they do not become part of the science curriculum at schools?
BTW, Carl Sagan was a real scientist that also wrote a sci-fi book. He is much more well known for his non-fiction books like the one I quoted from that gives good reasons why a rational, skeptical position and learning critical thinking skills is important for us as individuals and society and it is science class in schools where children are exposed to such ideas, often for the first time. Maybe you should read it, you might find it interesting.