Unfortunately, many of these people will not test their assumptions. Instead, they assume their assumptions are correct. This is unfortunate because faith in Jesus is built upon a mountain of evidence.
First, we are told in Colossians 1:16 that, “all things were created through him and for him.” That means that our Universe points to Christ. So for example, the Earth revolves around the Sun. Why? Because it points to the reality that we must revolve around the Son of God as the light of our lives (John 1:9). All humanity longs for marriage. Why? Because marriage is a symbol ordained by God to point to the union between Christ and His people. (Ephesians 5:32). Humanity longs for a King. Why? Because Christ is the Lord of lords and the King of kings. (Revelation 17:14). I could go on and on, but you get the picture.
In addition to this, God has arranged history (His story) around His Son. God promises the Seed of Eve (Jesus) will overcome the power of Satan. (Genesis 3:15). Jesus did this on the cross. God promises that through the descendants of Abraham (Jews) would come someone who would bless the families of the earth (Genesis 12:3). Jesus was Jewish. God promised a descendent of David would always be on the throne ruling over God’s people. (2 Samuel 7:16) Jesus was a descendant of David. Moses proclaimed a prophet greater than him would someday come to Israel (Deuteronomy 18:15). The most common description of Jesus by the people of Israel was that he was a prophet (Matthew 21:11, Luke 2:25, Luke 7:16, Luke 24:19, John 4:19, John 9:17). Once again, I could go on and on, but you get the picture.
In addition to this, Jesus is a historical figure. By this I mean He really existed, like you and I. No legitimate historian denies this, and no one denies that this is the same Jesus that the world follows. How is this evidence? Because of statements like this by Peter and John, “we were eyewitnesses of his majesty” (2 Peter 1:16) and “That which was from the beginning, which we have heard, which we have seen with our eyes, which we looked upon and have touched with our hands, concerning the word of life” (1 John 1:1). These two were not alone. There were thousands and thousands of eyewitnesses. This is the point of the book of Luke. Listen to how Luke begins: “Inasmuch as many have undertaken to compile a narrative of the things that have been accomplished among us, 2just as those who from the beginning were eyewitnesses and ministers of the word have delivered them to us, 3it seemed good to me also, having followed all things closely for some time past, to write an orderly account for you, most excellent Theophilus.” Luke was an investigator who accumulated evidence. He conducted interviews, compared facts, and placed it all in historical context. So many people have a wrong understanding of what the Bible is. It is at its core a history (His story) book. Once again, I could go on and on, but you get the picture.
If you want to go outside the Bible, check out Josephus’s Antiquities. Josephus was a historian and this is what he wrote about Jesus:
“About this time there lived Jesus, a wise man, if indeed one ought to call him a man. For he was one who performed surprising deeds and was a teacher of such people as accept the truth gladly. He won over many Jews and many of the Greeks. He was the Christ. And when, upon the accusation of the principal men among us, Pilate had condemned him to a cross, those who had first come to love him did not cease. He appeared to them spending a third day restored to life, for the prophets of God had foretold these things and a thousand other marvels about him. And the tribe of the Christians, so called after him, has still to this day not disappeared.”
So Josephus was just like Luke in the sense that he was someone who was reporting historical facts of Jesus as they played out before thousands and thousands of people. I always find it interesting that no one doubts the existence of Ceasar, but people doubt the existence of Jesus. Both lived at the same time, and the evidence of Jesus and his miracles are equal if not greater than Caesar (http://www.thegospelcoalition.org/article/sources-for-caesar-and-jesus-compared). Once again, I could go on and on, but you get the picture.
So what is the point? The point is this; don’t make assumptions about the blind faith of Christians. Faith in Christ is not blind. God through his mercy and grace has given us plenty of evidence. He has revealed his Son to us through many different means. I encourage you not to reject Jesus on a false assumption that there is no evidence, but instead explore what God has presented and make an informed decision. The best place to start is in the Historical Document called the Bible. Recognize what it is, a collection of 66 different books written by 40 different men over a period of 1500 years. All of it being evidence pointing to one reality; Jesus is the Son of God, the Christ.