Jesus Christ is often misunderstood. The phrase 'fully man and fully God' does not have biblical support; Christ's real nature is much more meaningful.
The Bible records that Jesus of Nazareth's Father was God and His mother was Mary, a human. What, then, was His nature? Was He a man? Was He divine?
Christ's sacrifice was not merely substitutionary, but representative, with Christ giving us a pattern for life - mortifying our flesh and putting out sin.
Baptism and being born again were already understood by the Jews, but the traditions had evidently blinded people to some additional spiritual nuances.
God's truth may bring about sadness, astonishment, anger, and bitterness to the one delivering the message. James and John were types of the Two Witnesses.