The question asks what is the effect on the perpetrators of their outrageous acts. So the answer can not be a repetition of their acts or how indigenous people felt; the correct option is that perpetrators lose respect for themselves (A).
Las Casas (1484-1566) was a Dominican friar who defended the dignity of the indigenous people of the areas Spain was colonizing. Being a religious man, he criticized perpetrators of violences highlighting how that violence was incoherent with God's teachings and how it meant these men lost respect for themselves.