You can explain away the plainly written word if you wish:
If WE(John is including himself in the we) claim to be without sin we deceive ourselves, and the truth is not in us
Anyway I understand this is subjective so we can just agree to disagree here.
Anyway, as I have said elsewhere, the Gentile church doctrine should be from Apostle Paul first and foremost. John, like Peter and James, were writing to their Jewish brothers. (Galatians 2:9)