The cruel symbolism that's in Barth being physically beaten with the book that hurts him spiritually is a great way to demonstrate the pain of an lgbt person growing up in a christian environment. It's a feeling of betrayal that grows with you, usually arising in childhood. You think about all the times you respected the rules while listening to masses about forgiveness and God's love, hoping that the sins you commit, by loving, can be forgiven in His eyes. But that's not how it works, so the faith gradually fades, giving way to self-love instead of guilt.
Perhaps a wound like this can be healed by a new perspective on religion, but it's unlikely. After a while, even masses of love and forgiveness begin to sound like an excuse to violence and repression.