A book on its own doesn't constitute evidence. It needs a lot more to verify it.
For example, lets take something older than the bible, lets take The Epic of Gilgamesh. There's different versions, but each account a story about the Uruk King, Gilgamesh. The Epic of Gilgamesh itself is not evidence that Gilgamesh once existed. We simply have a story recorded and told by many. In that story exists gods and giant monsters and man created from a meteorite (Enkidu), it involves a trip to the underworld and it involves an encounter with Utnapishtim, an earlier version of Noah, where he tells the story of the great flood.
We facts can I confirm with the story by itself? Absolutely nothing. It's a story.
Okay, now we discover some ancient documents, the Sumerian list of kings and we see clearly labelled, an era in the city of Uruk, King Gilgamesh. Okay, so suddenly it seems like Gigamesh might not be a fictional character, we can say there's a chance there really was once a man by the name of Gilgamesh who was king of Uruk. The list possesses some accuracies with other known kings giving it some credibility, though some of the dates are a bit messed up because some suggest people reigned longer than a human can possibly live. But then in the story King Gilgamesh is actually part-god, so it may suggest that if these dates were accurate, then maybe being part deity led to longer reigns.
What else do we have? We can cross reference the story with the bible and find huge similarities between the tale of Utnapishtim and the tale of Noah. The connection is further drawn to a close when you find that the abbreviation for Utnapishtim is Na'ish and use the pronunciation in Palentine at the time you'd get something along the lines of 'Noah'. So what does this suggest? That Noah somehow existed? If so, then why is there a heathen account of it first and not Jewish one? Why are the heathen gods accounted and not the one true God? Of course this isn't actually telling us a lot, because stories can evolve and they can be plagiarised. So we still haven't got verification that the Epic of Gilgamesh is in fact a true story.
The of course, a group of German archeologists managed to uncover a tomb where Gilgamesh's tomb is described by various ancient records. They couldn't confirm who's tomb it was with evidence present on site, however, it seems more and more likely that Gilgamesh was in fact a real live king.
I would argue this is more than Jesus has. Yet, what does it prove about the whole epic? If you wish to suggest BOTH the Bible AND The Epic of Gilgamesh are factual, then you will be in contradiction, because the Bible suggests there's only 1 God, whereas in the Epic of Gilgamesh there are many. There's also discrepancies between the story of Utnapishtim and Noah, both cannot be right, otherwise there were 2 separate floods, one initiated by God and the other by Mesopotamian gods and on both accounts an ark is built to sustain many animals.
But neither the bible or the Epic of Gilgamesh exist as evidence for anything except that they were written and there isn't enough supporting evidence either.
Would I turn around and say either are false? No. I would say either are highly unlikely or improbable. Why? Because they require a high number of assumptions for them to be true, many of which would contradict not only each other, but our understanding of how the universe works, things we have already have evidence for. It is simply not worth me assuming either are factual.
I think it's possible Jesus existed and I wouldn't be surprised if he did, however, for him to be who people say he is (the son of God) and do the things people claim he did, I would say it's highly unlikely for the same reasons as above. As for providing evidence for my lack of belief in things without evidence, it is ludicrous because I accept the unknown are a possibility, regardless of how improbable they may be and it would be logistically impossible, because everybody would have to justify their lack of belief in everything they lack belief in and there's simply not enough hours in a person's lifetime to do it because we are talking about many lifetimes of claims. You yourself would for example would have to justify a lack of belief in Ganesh, Odin, Ukko, Zeus, Jupiter and many, many, many other deities and it won't stop at deities either.