Just as we reject racism sexism ageism and heterosexism we reject speciesism. The species of a sentient being is no more reason to deny the protection of this basic right than race sex age or sexual orientation is a reason to deny membership in the human moral community to other humans.
Torture is such a slippery slope as soon as you allow a society or any legal system to do that almost instantly you get a situation where people are being tortured for very trivial reasons.