It's not that AIs will do worse things than humans have already done. It's that AIs will do those terrible things much more efficiently and with much lower risk to the people in charge.
I don't think you can hope for even that much. Rape has historically been systematically used for terrorizing the population in order to achieve military and/or political aims. An AI free from any ethical concerns could conceivably evaluate it as an efficient strategy for achieving some set of goals and proceed accordingly.