As a Christian, we should never be surprised by sin. Whatever tales, whoever falls - it should never surprise us. Sadden us - sure. Warn us - most definitely. Make us ready to forgive and care for the hurting - it should go without saying (but sadly, because of our own sinful hearts we need reminding).
But really, nothing that happens, no story that comes down the pike should ever be surprising. We have the Old Testament -- which is tale after tale of the people of God dropping the ball in horrendous ways.
Go read what Abraham does in Genesis 12 and following... not just the covenant stuff - the rest of it too. Or 2nd Samuel for David. After that - ain't nothing we hear about today surprising.
And we remain sinners in need of forgiveness.