"Made himself out to be" means that he revealed something about himself. In this case, he originally reassured his victims that he was only going to rob them, that he just wanted their valuables. This sort of tactic lulls the victims into a false sense of security - "If we give him our money and jewelry, he'll leave us alone." However, when he ordered his victims to strip and proceeded to rape the females, he revealed that he had lied about strictly wanting to rob them.
In the world of crime, there is something of a hierarchy, especially once one is in prison. Rapists are treated with contempt compared to burglars, thieves and robbers. Additionally, the penalties vary greatly when one is convicted of a robbery versus a rape.
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