LOL - yes it most certainly was! And Jesus was killed for it!
I think the motive of those who killed Jesus was different from the motive for Cain killing Abel.
"gnostic gospels that deny who Jesus is."
So who did the gnostics believe Jesus to be? Did they believe he existed at all? Did they or did they not believe he was the son of the one true God?
No, it is matter of man's views versus God's Truth. And that is the same reason that led to Cain killing Abel and Jesus being betrayed and crucified.
So who did the gnostics believe Jesus to be? Did they believe he existed at all? Did they or did they not believe he was the son of the one true God?
Different gnostics believe different things about Jesus, but all deny that He was God in the flesh. They say He was just a man, not God. Flesh is evil to most gnostics, so therefore, God cannot become flesh, which of course He did.
No they did not.