Should we eat meat? Or should we abstain from it? Do animals hold any rights? Or are they simply fodder for food and clothing products? If we eat meat or abstain from meat, it is here that we make our fundamental choice in whether or not we regard animals as moral agents, equal of moral treatment. Of course, I have yet to question the validity of the rights of non-humans.
If humans have rights, then certainly animals do. Racism is an institution that is nearly universally detested. This is not to say that there are no Racists. It is simply to declare that Racism, often considered to be judging on the color of one's skin (although there are other physical traits that vary depending on race), is wrong. This is declared insomuch that humanity is held as the highest of virtue and integrity. But why? If it is wrong to judge on race, then it must be certainly wrong to judge someone one the quantity of legs, especially if you withhold the right to their life solely on physical characteristics.
Of course, at this point before apologetics are proposed for relentless slaughter of denial of an objective morality, there are substantial claims that there is a difference between humanity and the rest of animals who dwell outside the scope of civilization. It is important to note, however, that a difference between humanity and non-humanity must be relevant. Just as the difference between a white man and a black man is skin color, this is not a relevantly important difference that would grant anyone the right to deny one rights or grant one privileges specifically on that physical trait.
There are many claimed differences between humans and animals. Humans have opposable thumbs, which grant us the ability to wield and create tools. We also have a thriving civilization of buildings and trades. Along with that, we communicate a large amount in our daily lives. The most important trait of humanity that pushed us to the global scale that we have now is that we have settled the land and farmed along with the important side-characteristic that our farmers overproduce more than they can feed themselves, thus opening positions for non-farmer tradesmen that can eat the farmers' produce, but grant a unique tool or trade to the community. Although there are many exceptions to these, such as the primates that can communicate with hand language and much of the upper mammalia have been noted to use tools such as bludgeons, it is not imperative that I bring such cases to point, thus showing minor - albeit passable - contradictions in the theory of human supremacy. The error of these distinctions between man and the rest of creation is that they assume these distinctions grant moral value. Non-human animals deserve the right to life and liberty not because of some privilege due to birth, but because they are sentient creatures. (Since much dispute can arise from the usage of the word "sentient," I will define it now as sensile, or capable of sensing one's environment.) A doctor may not slaughter someone of a lower profession, simply because he has the capability of healing people. Consequently, man may not slaughter (in terms of ethics) a non-human simply because he is superior in some manner of tool, civilization, or communication. As the logical and reasonable conclusion stands, man possesses no innate trait or characteristic that grants him moral worth over animalia (unless animalia would prove not to be sentient). A Racist is wrong for the making of judgments on skin color. A Sexist is wrong for the making of judgments of gender. A Speciesist is one who judges on species. The pattern is identical in all cases.
Since man and animal are now all within the realm of moral consideration of interests and no distinctive difference can be seen betwixt the two, there are certain apologetics for the slaughter of non-humans. Some may be quick to point out that animals eat each other, but it is important to notice that animals do many things, including rape (as a noted mating style of some of the smaller Galapagos lizards), cannibalism (as a necessary food source for fly larvae as well as 1/4 of the diet of salamanders), and theft (as noted among certain primates). If a lion killing and consuming a zebra justifies humanity killing and consuming a zebra, then - from the observation of the other workings in nature - may humans also rape, cannibalize, and steal from each other. One may point out that flesh has a desirable taste, but certainly, the taste of flesh cannot justify murder anymore than an orgasm can justify rape. There is certainly the call that if we do not consume animals, we consume plantae, but plants are not sentient beings, and therefore they do not fall into the realm of consideration. This is the case where one may assert that animals are not smart, but as demonstrated in the previous paragraph, intellect is not something required for moral consideration (and there is strong evidence to support that animals are intelligent beings that deserve more consideration than the status of puppets they are given now, although I will not present the detailed evidence as it is not necessary to the debate).
The only objection left to deny animals rights is the outright denial of an Objective Morality. Certainly, I suppose if we take into consideration our attitudes of animals that perhaps what we base our ethics on comes into consideration (or at least, to some, it is rather defined than considered). Although the topic of this subject is Animal Rights, I suppose it is necessary to some extent to digress into the foundations of our ethics, or our Meta-Ethics. Allow me to say that Subjective Moralities are not all-encompassing. In that, I mean if you declare your own ethics on some Existentialist point is useless as they are not objective in any sense, and therefore they are not universally applicable to all. The Objective Morality I propose is based on a universal consideration of interests. One may be quick to point out, "But this is 'your' Objective Morality." And the point is clearly made. However, I must denote that whether or not everyone agrees with a morality, it does not make it any more or any less objective. Just as science is objective, whether or not everyone agrees or disagrees with it. The opinions of the masses may waver all that they wish, but that does not make science any more or less objective. The Objective Morality I propose is based on the consideration of sentience (previously defined). I seriously doubt that any Jewish person in a concentration camp would admit that there existed no Objective Morality. If anyone suffers (not necessarily directly linked to pain, although linked in certain cases), they will know that suffering committed upon them is immoral. And from this suffering we derive a knowledge that it is immoral and in this observable and demonstrable method, it is objective. I hope all of the readers will excuse the poor defense given in the right of Objective Morality, but it is one of several (and perhaps the most important) objections to granting animals the right to life and liberty. For more on this Objective Morality, please see here...