Why is every person under condemnation from birth?
Condemnation rests on every son of Adam because all people are born into the Adamic race as sinners. Scripture declares all have sinned and come short of the glory of God, so every person inherits Adam's fallen condition from birth. That universal sinfulness is why condemnation is already resting on those without the Son.
Les teaches that condemnation rests upon every son of Adam. He explains that we are born sinners into the Adamic race, and that this is what Romans has been showing: all have sinned and come short of the glory of God. We are all sons of Adam, all sinners, and under condemnation. Les also recalls Jesus' words in John's Gospel: he that hath the Son hath life, he who hath not the Son hath not life, and condemnation is already resting on him. Then Romans 8 declares, "There is therefore now no condemnation." Les asks what made the difference, and answers: the Gospel.
There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.