First off, this probably belongs in Philosophy, rather than Ethics and Morality.
Secondly, 'historical gospel' is not evidence any more than 'Little Red Riding Hood' is evidence for the existence of speaking, anthropomorphic wolves capable of imitating old women. Without ample physical evidence to back it up, the legitimacy of an old book as a source of truth is laughable. Even if a few parts of a story have a basis in truth, that does not mean the rest of the story does as well. For example, we know that the city of Troy existed, because we have found said city, but it would be foolish to assume that Scylla, Circe, Amazons, Cyclops, Achilles, Ares, and Athena all also existed because they are referenced in the same very, very old story.
Thirdly, it requires no faith to be an atheist. Religious people often seem to have trouble understanding this, and will go so far as to call any kind of assumption 'faith' in order to justify their own beliefs. I assume the sun will come up tomorrow. I assume that unicorns don't exist. I assume that ice cream will be cold, boiling water will be hot, and tides will follow a predictable pattern based on the revolution of the moon around the earth and the earth around the sun. I also assume there is no god, because I haven't seen any evidence of one. I assume we have all of these things in common except one, and to single any one of them out and call it a 'faith' is to stretch the meaning of that word until it encompasses any thought or concept and is rendered meaningless.
For more clarification in a ear-caressing english accent, please enjoy the following videos:
YouTube - Lack of belief in gods
YouTube - Putting faith in its place
YouTube - Critical Thinking