you are simply wrong...
1 John 3:7-15
King James Version (KJV)
7 Little children, let no man deceive you: he that doeth righteousness is righteous, even as he is righteous.
8 He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil.
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.
I'll just quote from John and leave it at that:
1Jo 1:8 If we say we have no sin, we deceive ourselves, and the truth is not in us.
And John is certainly talking to Christians and about himself as well. The difference between the version of 1 John 3:9 ("he cannot sin") and 1 John 1:8 ("if we say we have no sin") can be found in this verse:
1Ti 5:20 As for those who persist in sin, rebuke them in the presence of all, so that the rest may stand in fear.
Every true Christian still sins but doesn't persist in sin. Every non-Christian doesn't care. If there are tares among the fold who are persisting in sin, then we should call them out simply so that true believers are reminded of the gravity of sin. And we should stand in fear when we sin. Fear not of losing our souls but fear that we should dishonor God and rightfully bring down corrective measures on us. We are His ambassadors and we represent the King. We are to behave accordingly.
Please...Please...Please actually study the scripture. And this isn't just me...but every theological scholar going back eons...and Greek scholar...regarding 1 John 3:8/9...
It is VERY clear from the entire context of 1 John...in conjunction with Pauls words in Romans 7...and with the fact the Greek renders "hamartanein" CLEARLY...and also in unison with Romans 6:1.
It means the act of habitual sin as if we aren't impacted by our salvation. Same concept is found in Romans 6:1...where Paul is speaking to CHRISTIANS. "Shall we continue in Sin so grace may abound?" Implying that beleivers CAN. NO! is the answer. It is a process of sanctification. Again, John is clear in 1:8...you deceive yourself if YOU say you have NO sin. Paul says HE STILL has sin.
It all has to line up without contradicting itself...and frankly...your interpretation fails that standard. You cannot get around Romans 7 and Paul's confession.