When the old man sins, the new man is not even in operation, is what I'm saying.
1Jo 3:9, Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God.
This is talking about the whole person, not just the spirit-man, or, the new man.
Now, I know that this (sound) doctrine might offend you; because it means that if you continue to sin in the flesh, you are not born of God.
I would say that many people look at this scripture the wrong way.
They say, "I believe that I am saved; but I sin; therefore this scripture cannot be saying that the born of God cannot sin."
Instead of holding the scripture as supreme and saying, "This scripture says that the born of God cannot sin; and therefore, if I sin, I must not yet be born of God."