It's not about the motivation for the act but the nature of the act. The fact that killing someone in self defense is permissible is proof that the act of killing someone is not intrinsically evil. And these acts are in contrast to acts that are intrinsically evil. There are no circumstances whatsoever in which, for example, rape would be permissible.
rape, by the very nature of the act, is never permissible as a means to an end -- whereas killing is, in some circumstances, a moral act.
therefore, we can conceive of God commanding us to kill, but not to rape.
this is probably the technically correct debate answer to the AIDSfaggot