[dragonwriter]

> Then is torture, rape and murder wrong because the victim is sentient, or because the perpetrator is?

Nothing is wrong unless it's done by a moral actor (which is a much higher standard than sentience. Pretty much everything with a central nervous system is sentient, but lobsters, for instance, are not moral actors.

Similarly, the usual understanding of the moral status (the gravity of not the binary permissible/wrong status) of the three acts you describe is somewhat connected to the target as well as the actor being a moral actor (that's least the case with torture, and most the case with murder) rather than merely sentient.