Science is not supposed to be a religion but a method of inquiry. It is a way to ask questions of nature or the universe (or GOD) and get reliable answers. The answers are so reliable that almost all of the "progress" of civilization is based on it. Scientific method consists of 2 basic points 1- publication and 2- replication.  Scientist should publish their observations "This is what I saw..." and their theory... "this is what it means, how it works, how to predict it, etc."  Other scientists can then test the truth of the publication by duplication the work.

Scientific method easily discovers easily repeatable phenomena.  This is a large body of knowledge, but not every thing, not every truth in the universe is a repeatable phenomena.  There are other observable and describable phenomena that are alas, not repeatable.  There is even a respected if often humorous publication call the "Journal of Irreproducible Results"  which has had respectable articles by respected authors like Lt. Governor Bill Hobby on a particular Texas Legislature.

Because science and scientists have for so long associated science with the TRUTH, and non-science (like astrology) with non-sense, they have trouble seeing that there is more TRUTH out there than what can be easily observed, described and consistently repeated.  The scientists are correct if they say the un-scientific truths are unreliable. But they are wrong to deny the possibility of such truths. 

Science becomes a religion when there are bodies of phenomena which are taboo for scientists to study.  UFO's, paranormal phenomena, religious phenomena lead the list. Few scientists will choose to be associated with serious study of any of these topics, out of fear of loss of credibility. Dr. Sagan's book "The Demon Haunted World" is a refutation of popular culture's acceptance of lots of pseudo-scientific popular myths. It is devastating to those who believe in alien abductions, etc.  It tries to explain the phenomena of honest people who honestly believe they saw aliens or the virgin Mary.  While the book does not go so far as to try and discredit ordinary religious experience, it does discredit, at least by implication, miracles.   A weakness of the book, of Dr. Sagan, is that he never accepts the possibility of any other kinds of truths than hard scientific observational, repeatable Truths. I fear he never had or was afraid to admit having a religious experience.