@Johann
A Christian has the Spirit, and the flesh, so technically by having the Spirit he is not in the flesh Rom 8:9
9
But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his.
Those Corinthian believers, though they acted carnally, nevertheless they had the Spirit, Paul mentioned that of them 1 Cor 6:19
19 What?
know ye not that your body is the temple of the Holy Ghost which is in you, which ye have of God, and ye are not your own?
So your argument doesnt help you with Rom 8:8 at all, those who are in the flesh dont have the Spirit dwelling in them like believers do