If we have the right to kill, why don't we have the right to torture?
They are different things that inflict a different amount of suffering and distress on a creature capable of feeling suffering and distress.
The nature of torture aside, taking the life of a sentient being is the ultimate violation of its rights. I don't see how any act less than killing can be considered morally worse than killing.
This does not make it right for a human to deliberately cause harm to an animal for pleasure or entertainment. I also would consider trophy hunting to be immoral if one leaves the body to rot.
Why?