You are likening divorce to the unpardonable sin, and that's a YUGE gaffe. First off, the OP was talking about a lost person, and Paul said because the mind set on the flesh(in context this is the lost folk) is hostile toward God; for it does not subject itself to the law of God, for it is not even able to do so, 8 and those who are in the flesh cannot please God.[Romans 8:7]
The lost are not subject to God's Law, and can not even begin to keep them. The bible does not take effect in one's life until AFTER they are saved. You are expecting the lost to live up to the righteous demands in the bible, when they can't. The only reason we can is because we have been imputed ALL of the Christ's righteousness, and the Father sees us through His Son.
All the lost live under is the Law, and they are condemned as Law breakers. However. Christ redeemed us from the curse of the Law, having become a curse for us--for it is written, “CURSED IS EVERYONE WHO HANGS ON A TREE”-- [Galatians 3:13]
So, I will go with Paul and not some self-righteous Pharisee setting upon a Sanhedrin.