We believe because we MUST believe. God has created faith in our hearts, and taught us that His Word is true. They were judging Jesus by their feelings, their prejudices, their opinions and most of all by their lack of saving Faith. So they ended up rejecting the Son of God. Instead of inviting Jesus and God's Word to sit in judgment over them, they decided to sit in judgment on Jesus and on His Word.
People today do exactly the same thing.
Before they even began, they decided that the Bible is NOT the Word of God, so they can cut it up as they please. Christians don't cut up the Bible. Christians don't sit in judgment on the Bible, but they allow the Bible do judge them, their thoughts, their faith, and their actions. They are using Scripture to prevent you from doing what is right, just as Satan tried to do with Jesus 2000 years ago. We live in an age of spin, of exaggeration, of deception and of the outright cleverly worded lie.