No one is a sinner "because" they are born. We are simply born in the state of sin. I don't think any Catholic would say one is a sinner because of birth.
This is such a serious theological issue, that we should not try to find faulty compromises.
Augustine of Hippo (354-430) taught that Adam's sin is transmitted by concupiscence, resulting in mankind becoming a massa damnata (mass of perdition, condemned crowd
Actually, this would need another thread, unless we would specifically want to discuss anything Vladimir Moss said on that issue.
I don't think I'm compromising anything. I think some of these teachings exist in St Athanasius and St Cyril of Alexandria. When we are born, we are born "exiled", separate from God's grace to a certain extant, in a state of sin. In our Coptic liturgies, we pray "even if one's life may be just one day, he is still not without sin." We all fall short of the glory of God. Nevertheless, by partaking of His glory, our exile, our state of sin is abolished, our disease of sin is cured, and our continuous sins are forgiven, and our lives continue to become illuminated.
Perhaps we can discuss St. Augustine in another thread. Let's just stick with Moss. Can you quote anything from Moss that bothers you?