Jesus is sinless because he is God. Not having a human father has nothing to do with it. "Brand Y" is confused, muddled, and dabbling with heterodox Christology, as usual.
Campion:
The Christological problems with many of the FR Prots shows its head again. Christ is eternally begotten of the Father, hence His Divine Nature by definition is sinless. He was incarnate of the Virgin Mary so Christ the Eternal Word of The Father is incarnate of the Virgin Mary and becomes Man. THus in that context, we now understand Christ, the 2nd Person of the Most Holy Trinity as a 1) Divine Person with 2 Natures. These 2 Natures are 1) Divine, which is sinless as Christ is Truly God and 2)Human Nature, which he received from Mary, thus the question now remains, how was Christ the perfect Man with respect to his Human Nature.
Christ as the 2nd Adam is the perfect man, his human nature is what God wanted for Man before the Fall. Thus, God in his infinite wisdom chose Mary as the perfect ark or vessel through which Christ would become incarnate. The Immaculate Conception thus speaks of “GOD” acting in a power way in Mary’s life and giving her an abundance of Grace as the Old Douay Rheims translation puts is “And the Angel said to her: Hail Full of Grace, the Lord is with thee, blessed are thou among women......Fear Not Mary, for thou has found Grace with God” [cf Luke 1:28-30].
So in what context does Mary have God’s grace before CHrist’s passion, death and resurrection, it is because God can work outside of time and the benefits of CHrist death and resurrection were given to Mary so that her will conformed to God’s will and she became God’s instrument in the plan of salvation in that Christ became incarnate of her. Mary’s being in a state of Grace if why Christ “human nature” was not tainted with original sin and the author of Mary being in state of Grace is God working in a mysterious way to provide Mary with said Grace.
Lots of Nestorian heresy here among the FR Protestant brigades.
Therefore He would not be qualified as a substitutionary atonement for the sin of all mankind, hence no real Gospel message exists.
Reductio ad absurdum,...wrong basis for His sinlessness.