I wouldn't say blind or deaf, I'd say they aren't historically literate though. I don't think there is any doubt that Jesus did exist, he was very much a person. The question is whether or not he was the son of god.
Serious question though, what makes Christianity more valid than say, Islam? I mean, all of the major world religions share a lot of similarities, so all of the arguements used to prove the existance of a Christian god, can also be used to prove the existance of many other gods.
The Hebrew god, Christian god and god of Islam are all the same one and only God (of these religions which I too share). The differences heirin primarily center around treatment of Jews, whether or not Jesus was a heritic, a prophet or the physical embodiment of God and the specific religious laws and the conviction of adherence to them.
Historically however Jesus was for certain on this earth and many of his works and most of his life are well documented by multiple religious and secular sources. As was Mohammed, Abraham, King David, Soloman and more. Interesting tidbit is that the Hebrew bible (old testament/Torah) has one of the oldest references to China which is later supported in the Christian new testament.
Whether you believe it is coincidence or in fact a richer history for these religions than is known today contradicting the alleged age of these religions here is anecdotal evidence of the deeper relationship which scholars secular and religious alike are studying:
http://www.ocf.berkeley.edu/~wwu/chinese/bible.shtmlNot to mention many of the "myths" of these religions, at least to modern secularists, are cosupported within the "myths" of other religions and secular account as well as modern discoveries which confirm anamolies and practical facts about these stories. Namely such things as the great flood supported by many religions and scientific fact in soil analysis in finding aquatic matter and life in places they should not have been and seeing that chronologically intermingled with land based matter/life indicating that great portions of dry land were in fact covered by water at some point in earths history and such things as the battle of Jericho which was at one time deemed impossible due to theories that placed Jericho being destroyed prior to the emergence of the israelites and later more recent archeological evidence dating it to well within the time of the Israelites, along with the modern discovery of harmonic resonance which scientifically could allow for the felling of the walls of Jericho and there is historical account that the marching around the city prior to attack was in fact used by secular armies as well to lull a well defended enemy into a sense of false security.
Take it or leave it, much of the religious texts of these sister religions is supported by known scientific facts/discoveries, arhaelogical evidence and seemingly inconsequential global accounts in disperate geographies, religions and peoples. For the non-believers it seems like you'd rather discount science and fact which is supportive of the factual basis of these texts in some vain arrogance that somehow religion is an afront to the very "science" worshiped by said people. Not to mention that evolutionary sciences such as DNA evidence do account for a remarkably shorter time on the earth for humanity than what early evolutionists theorized as well as a genetic bottle-neck for humanity (great flood?) As well as a remarkable alignment to the original story of genesis with evolutionary development (with much of the texts of these books being told in parable to express an understanding to peoples with little more knowledge of the mechanics of their world than we have today.... remember to "With the Lord a day is like a thousand years, and a thousand years are like a day." So time quotes such as the 7 day creation story were quite probably not 7 human days as time would not operate the same as we experience it... Didn't Einstein and several other "worshipped" scientists show mathematical evidence of the probabilities of said time phenomena in our universe related to gravity, speed and mathematical evidence of the probable existence of multidimensional "planes of existence")