Facts: The Priory of Sion is a complete fabrication invented by a political radical in France in the 1950s. In a recent edition of the CBS News program 60 Minutes, Ed Bradley follows the trail of this elaborate hoax and shows it to be completely false.  (http://www.cbsnews.com/sections/60minutes/main3415.shtml)

In their article, Facts vs. Fiction in 'The Da Vinci Code', Carl E. Olson and Sandra Miesel state, “A frequent question asked by readers of Dan Brown's The Da Vinci Code is, "How much of the novel's depiction of historical events, people, artwork and institutions is correct?" The short answer is, "Not much." 

In fact, "the only thing more amazing than Brown's consistent misrepresentation of facts is a widespread acceptance of his claims, with both reviewers and readers praising the "research" and "knowledge" supposedly evident in his novel.” (The Da Vinci Hoax: Exposing the Errors in "The Da Vinci Code")

In an interview with Sandra Miesel, she was asked, “What is it about The Da Vinci Code that you find so distasteful that you’ve written a book about it?” 

She responded, ”The sheer falsity and stupidity of The Da Vinci Code would have given me enough incentive to rebut it, quite apart from its anti-Catholic slant. As a trained historian, I was outraged to see so many errors between two covers, errors naively taken as absolute fact by vast numbers of readers. I wrote to defend truth and Christianity.” (From the Focus On The Family website: http://go.family.org/davinci/content/A000000090.cfm)

A quote from Fred Sanders: "As an amateur art historian, I should be thrilled that a major movie is putting Renaissance masterpieces in front of mass audiences. Yet I find myself having the opposite reaction. As one art historian summarizes, "The author's grasp of the historical Leonardo is shaky." (Art, Truth and 'The Da Vinci Code' — Separating Fact From Fiction by Fred Sanders)

Galatians 1:6-9

⁶I am astonished that you are so quickly deserting the one who called you by the grace of Christ and are turning to a different gospel— ⁷which is really no gospel at all. Evidently some people are throwing you into confusion and are trying to pervert the gospel of Christ. ⁸But even if we or an angel from heaven should preach a gospel other than the one we preached to you, let him be eternally condemned! ⁹As we have already said, so now I say again: If anybody is preaching to you a gospel other than what you accepted, let him be eternally condemned!

"My dear," Teabing declared, "until that moment in history [The Council of Nicea in 325 AD], Jesus was viewed by His followers as a mortal prophet . . . A great and powerful man, but a man nonetheless. A mortal."

"Not the Son of God?" [said Sophie]

"Right," Teabing said. "Jesus' establishment as 'the Son of God' was officially proposed and voted on by the Council of Nicaea."

"Hold on. You're saying Jesus' divinity was the result of a vote?"

"A relatively close vote at that," Teabing added.

“It was all about power,” Teabing continued. “Christ as Messiah was critical to the functioning of Church and state. Many scholars claim that the early Church literally stole Jesus from his original followers, hijacking his human message, shrouding it in an impenetrable cloak of divinity, and using it to expand their own power." (DVC, Page 233)

Reason #1: All four New Testament Gospels teach the Divinity of Jesus and were written in the first century.

John 20:27-31

²⁷ Then he said to Thomas, "Put your finger here; see my hands. Reach out your hand and put it into my side. Stop doubting and believe." ²⁸ Thomas said to him, "My Lord and my God!" ²⁹ Then Jesus told him, "Because you have seen me, you have believed; blessed are those who have not seen and yet have believed."

³⁰ Jesus did many other miraculous signs in the presence of his disciples, which are not recorded in this book. ³¹ But these are written that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name.

Mark 2:5-7 -- Jesus Claims Authority to Forgive Sin

⁵When Jesus saw their faith, he said to the paralytic, "Son, your sins are forgiven." ⁶Now some teachers of the law were sitting there, thinking to themselves,   ⁷"Why does this fellow talk like that? He's blaspheming! Who can forgive sins but God alone?"

⁶³ The high priest said to him, "I charge you under oath by the living God: Tell us if you are the Christ, the Son of God."

⁶⁴"Yes, it is as you say," Jesus replied. "But I say to all of you: In the future you will see the Son of Man sitting at the right hand of the Mighty One and coming on the clouds of heaven."

⁶⁵Then the high priest tore his clothes and said, "He has spoken blasphemy! Why do we need any more witnesses? Look, now you have heard the blasphemy."

Romans 10:9, 13

⁹If you will confess with your mouth, "Jesus is Lord," and believe in your heart that God raised him from the dead, you will be saved ... ¹³"For everyone who calls on the name of the Lord will be saved."

Philippians 2:5-11 -- A Hymn That Contains Four Statements on the Divinity of Jesus

Every tongue will confess that Jesus is "Lord." Thus, this hymn states that Jesus existed in God's form, was equal to God, will receive the same honors that God allows only for himself, and possesses God's name. What he lost when he emptied himself and descended to Earth will be restored to him. Accordingly, when Paul's writings and the four New Testament Gospels are considered, we may regard it as historical bedrock that the first-century Christians viewed Jesus as divine. (Source: http://go.family.org/davinci/content/A000000096.cfm)