They are, in fact, evil in concept. St. Laurence misinterpreted this as the poor gave money to the church for relics and forgiveness. Salvation can be sought for through the church as it has been granted this by Christ. It is clear that the power of the church is adequate, by itself, for the forgiveness of sins. The main treasure of the church should be the Gospels and the grace of God.
Indulgences make the most evil seem unjustly good.
Therefore evil seems good without penance or forgiveness. The treasured items in the Gospels are the nets used by the workers. Indulgences are used to net an income for the wealthy. It is wrong that merchants praise indulgences. They are the furthest from the grace of God and the piety and love of the cross.