According to Allaah's words in Qur'an, it is a greater sin to oppress than to murder. If you murder, the person's soul goes on to the afterlife, they cannot be tortured nor harmed by you. To molest or rape is to oppress that person for years, even if you only do it to them one time. You have caused trauma that will haunt them and cause them great emotional misery. It is a worse sin to doom the child to a life of pain.