KJV really has nothing to do with it ... every reputable translation includes the trinitarian formula in Matthew 28.
Further, even without it the doctrine of the Trinity is firmly established ... not by any isolated proof text, but by the overwhelming testimony of the whole of Scripture.
The doctrine of the trininty has more holes than a collander at a shot gun range.
The Bible CLEARLY says that there is one God and one mediator between God and man, the MAN Christ Jesus.
God is invisible. Jesus was visible.
God is without begining and Jesus had a 'genesis', a birth, a beginning.
God is not a man that he should lie, nor the son of man that he should repent. Jesus was/is a man and was repeated referred to, even referring to himself as 'son of man'.
Jesus is the IMAGE of the invisible God.
If Jesus was God, then Jesus clearly promised that believers would do greater works than God because, he (Jesus) would go to his father. (If Jesus is God then who is the son of God? Jesus?)
God cannot be tempted with evil yet Jesus was tempted in all ways...
So before you yahoos start in with your John 1:1 stuff, answer the CLEAR as written and in context words from the Bible.
Let the dead bury the dead. The living have work to do. I suspect the amount of demonic delusion that goes into the denial of the central fact of the universe (The Trinity) makes those who succumb to that denial immune to reason.