We support the promotion of a true, good, and pleasant life for all life and the removal of all which causes suffering to the same. In particular this extends to animal welfare; as Jeremy Bentham wrote: "The day may come when the rest of the animal creation may acquire those rights which never could have been withholden from them but by the hand of tyranny... What else is it that should trace the insuperable line? Is it the faculty of reason, or perhaps the faculty of discourse? ... The question is not Can they reason?, nor Can they talk?, but Can they suffer?"
Roger Scruton, who writes that only humans have duties, and therefore only humans have rights. This assumes that rights come from duties; as we have illustrated rights come from a an equality of consideration of interests. Where this consideration does not occur, speciesism - this does not argue that all species are equal in ability, reasoning, etc, and nor does it suggest that an equality of rights must be universally applied. It is not in an animal's interest to vote, etc., but it certainly is in their interest not to suffer. (c.f., Peter Singer, Practical Ethics)
Nonsense oppositional argument from Objectivists (Leonard Peikoff . Objectivism: The Philosophy of Ayn Rand, 1991), p. 358) "By its nature and throughout the animal kingdom, life survives by feeding on life. To demand that man defer to the "rights" of other species is to deprive man himself of the right to life. This is "other-ism," i.e., altruism, gone mad." Because apparently being a vegetarian will kill you!