It's not that hard. The definition of reason is to "think, understand, and form judgments by a process of logic." The definition of objective is "not influenced by personal feelings or opinions in considering and representing facts." If we are concerned with coming up with factually correct views of the universe, as opposed to emotionally-based (the definition of objective), we cannot use subjective, emotional ideas and opinions (again, the definition of objective) to support pre-existing emotional beliefs, based on nothing but blind faith. One of the core concepts in objective science is falsifiability. You must be able to examine your positions and experiences to see if existing knowledge has falsified them, and also, you must be able to conceive of a set of facts that, if found, would falsify your position or experience. If you cannot, you are not doing science. You are not using reason. You are not operating objectively. All of these things are not done with religion. It is inherently irrational by its very nature.