I've heard a number of people try to reconcile Christianity with non-Christian traditions by saying that Jesus was a great teacher/prophet/moral authority, but was not the divine son of God.

My first objection is that if you read the Gospels in their entirety, you find that Jesus explicitly claims to be divine numerous times.  This has in the past been attributed to historical inaccuracy.  However, if the Gospels could be wrong about such a significant detail, than they couldn't possibly be a reliable account of his other teachings.  If the claim of historical inaccuracy is true, than any references to his teachings based  on the Gospels themselves is rendered invalid, and we really don't have enough information about Jesus to discuss his status as a teacher or prophet.

Many of the members here have probably heard the argument that if Jesus was not divine, he was either insane or simply lying.  My claim is that neither of these cases should allow Jesus to be thought of as a moral authority.  Someone who can believe in such grand delusions  as being the son of God does not even grasp reality, let alone teach subtleties of it such as morals.  And obviously, someone who would lie about his divine status contradicts almost everyone's idea of ethics. 

Both of these objections rest on the same principle.  Jesus did claim to be the son of God (I realize that not everyone agrees to this statement; there are other discussions debating it).  If he or any source recording him could be wrong about such an important detail, the source cannot be held as reliable.  This doesn't prove whether Jesus was divine or deluded, but it does demonstrate why there is no middle ground.