Obviously, ruty - I mean, Rowan Williams has about fourteen brains and he still manages to be a liberal. A better way of putting it would have been to say that I believe it to be intellectually dishonest - others, including those with far more knowldege than I could ever have, will believe differently. When I was a liberal an accusation I often used to get was that I believed the nice bits and ignored the bad, and in the end I couldn't argue with that b/c basically it was true. That's not to say I disbelieve the Bible b/c I don't. I just start from a position of doubt and then look for ways to be convinced. Some things convince me, others don't.
Madamez, you are right, there were several men thought to be the Messiah. One called Simon something (knackered brain gone blank) was the type of Messiah the Jewish people thought they were going to get - his armed rebellion was extremely successful and for a while he caused the Romans no end of problems, until he and his army were massacred. Jesus was different in that his message was of peaceful dissent. 'Going the extra mile', for example, wasn't a position of weakness. A Roman soldier could demand that a Jewish person carry their goods for a mile. 'Going the extra mile' could have got the Roman into trouble with their own authorities.
One reason I believe that Jesus was a real person is that, once you strip away all the stuff the evangelists added in order to make their own particular points, you get a clear and consistent picture of what Jesus was like. There is also the consisten source, Q, used in the Synoptic gospels. You might be interested in the work of the Jesus Seminar, a group of scholars - I think they number over a hundred - who vote on what they think Jesus actually said. Some are Christians, some aren't. The results are very interesting - the whole of John's Gospel is ruled out, for example. Geza Vermes, who is Jewish and one of the best Jesus scholars in the world, is also worth a look. He sees Jesus as a prophet, nothing more, but does not deny Jesus' existence. He has a great postscript in o0ne of his books where he dreams of Jesus coming back and being astonished at teh faith that has sprung up around him. In his dream, Jesus tells his followers that they can keep their rituals if they like, but to rely on themselves for guidance as to knowing what is right.
Incidentally, given the locality where Jesus is likely to have been born, Vermes thinks Jesus would have been short and thick-set.