Consider this verse: 2 Cor 7:1
Since we have these promises, beloved, let us cleanse ourselves from every defilement of body and spirit, bringing holiness to completion in the fear of God.
This makes it clear that our spirits need to be cleansed from defilement as well as our bodies and this is directed to saved people who are born again / have a born again spirit. Therefore it is not good hermeneutics that he is presenting when he says that our spirit cannot sin. This verse destroys his argument. Careful what you hear. The "our spirit cannot sin and is not guilty no matter what we do with our body" teaching has been in the church from the beginning and is what the Nicolaitanes might have taught according on one the church fathers who wrote about them centuries later. No one really knows what they taught but the fact that this "your spirit cannot be guilty of the sin of your flesh' was blamed on them early in church history reveals how ancient this false doctrine is. The same demons that were behind it then are still active. They are using new teachers and dressing it up but it is the same old ancient Epicureanism syncretic falsity.
And also this one:
1 Corinthians 6:20
For ye are bought with a price: therefore glorify God in your body, and in your spirit, which are God's.