Few tragedies can be more extensive than the stunting of life few injustices deeper than the denial of an opportunity to strive or even to hope by a limit imposed from without but falsely identified as lying within.
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.