Your analogy is flawed. The theory of the big bang (and scientific theories in general) was developed to explain pieces of evidence we have collected about the universe, such as the fact that the universe is expanding, etc. Scientific theories are revised, refined, or even thrown out when new evidence is found that contradicts the theory.
Now contrast the process of scientific discovery with religious teachings. All religions, not just christianity, have stories about how the earth and people came to be. When new evidence is discovered, for instance, evidence that points to evolution, do they revise their story? Are they willing to start over and say, it looks like we got that one wrong? That was a rhetorical question. We know the answer is no. They cling to their creation story no matter the mountains of evidence showing that it can't be true.
Now who is dogmatic?