Which is a Christian:
1 John 1:8 and 10
8 If we say that we have no sin, we deceive ourselves, and the truth is not in us.
10 If we say that we have not sinned, we make Him a liar, and His word is not in us.
or
1 John 3:9
9 Whoever has been born of God does not sin, for His seed remains in him; and he cannot sin, because he has been born of God.
Can't you see that 1 John 1:8 and 10 go along with verse 6. They are all BEFORE Christ. They are all walking in darkness and have never been cleansed of ALL sin.
No, you cannot create a division like that in 1 John 1. From the very first verse, it's clear that John is speaking to believers on Christ Jesus. You can't make an excuse to serve the Hyper-Grace theory just because you don't understand the 1 John 3:9 verse.
1 John 2:1-2
2:1 My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:
2 And He is the propitiation for our sins: and not for ours only, but also for the sins of the whole world.
KJV
Even in that above Scripture John is showing us what to do when we as believers do future sin.
1 John 2:3-6
3 And hereby we do know that we know Him, if we keep His commandments.
4 He that saith, I know Him, and keepeth not His commandments, is a liar, and the truth is not in him.
5 But whoso keepeth His word, in him verily is the love of God perfected: hereby know we that we are in Him.
6 He that saith he abideth in Him ought himself also so to walk, even as He walked.
KJV
Just as Paul spoke of walking by The Spirit in Gal.5, John also gives us an example with following Christ's commandments, and thus showing a walk in Him.
So the whole matter is our 'walk', and that's a day by day thing, not "well I believed already, so my walk is already done for me" type of attitude.
The key to interpreting the 1 John 3:9 verse is the following...
1 John 3:6
6 Whosoever abideth in Him sinneth not: whosoever sinneth hath not seen Him, neither known Him.
KJV
So how... do we abide in Him?? By just 'thinking'... we can't sin anymore and thus have no need to repent to Him anymore? Certainly not! John was specific about our Lord Jesus being our Advocate to The Father for us when we sin. If a believer thinks they don't or cannot sin anymore, then they have NO Advocate in their behalf. Know what that means? It means the iniquity we might commit after having believed is NOT covered, as we have to stand before God as our own advocates! I'm sure you can fathom how that would work out.