Believers take it as one source too. How else do you come up with a 6000 year old Earth?
The bible has a few historical events and people take it seriously. It's akin to stuffing today's newspaper into the middle of book of short stories and calling the collection factual.
I'm not seeing the relevence in your statement to the topic at hand. Do you have something actual constructive and informative to say on the topic, or did you just come into the thread to try and troll religious people. Aftearll we aren't talking about if the entire bible is factual, just simply one aspect of it, the existence of jesus.
If I were to take chapters from Bill Clinton's biography, and mix them with various dr sues books, it wouldn't suddenly make Clinton's biography fictional.