Ok so you're a moral subjectivist then whereas I believe in objective morality so we fundamentally disagree there, but I don't think that really matters in the case of this argument. It is immoral to use animals to our own benefit but to their demise because there is a victim in this act. We should extend similar moral consideration to animals because they feel pain and have a will to live as we do. It does not matter that they are less intelligent just like it it is not justifiable to kill a human who is less intelligent, such as someone who is mentally retarded or has similar impairments. They desire a life without suffering and exploitation and therefore we should not deprive them of that considering we don't have to. Using history and nature as a justification is a fallacy as we have committed many unjustifiable acts in nature as do many animals, such as rape, cannibalism, exploitation and the enslaving of fellow humans. This does not make those acts moral, as we have refined our thought and evolved beyond accepting those behaviours as "part of nature" and "the way of the world" as we should with eating/exploiting animals. We have moral agency unlike lions who kill without thought, and we also can live healthily without meat which lions can not. Where you claim it is hard to argue against animal exploitation I would counter that it is almost impossible to argue for the consumption of animals on a moral level in modern civilised society.

You have stated that in the case of a Mediterranean diet it is morally justifiable to kill animals to eat them, but provided no argument or evidence supporting the stance. I reject the notion that there is an ethical source of meat. While I agree that the Mediterranean is healthier than the standard western diet, I think it is also at this point incontrovertible that you can live healthily on a vegan diet, therefore the killing of the animal is unnecessary and therefore unjustifiable.

You don't have to think the value of a human and a cow are on par with each other to agree with the ethics of veganism. It is more to the point that the moral value of a cow is worth more than the temporary pleasure you get from eating its body.