Catholic church used this custom of selling indulgences throughout Middle Ages which was in one moment unacceptable even to some people in the church. That is why Luther and people similar to him started opposing it. Luther showed his dissatisfaction when in 1517 he wrote 95 Thesis and openly protested against indulgences. His fight, with the support of others at the end led to creation of Protestant churches, including the Lutheran church.
Muslim nobles subjected most Muslims to a miserable, difficult life of serfdom. Christians from the Byzantine Empire continually tried to convert Muslims to Christianity.
