Let us be the first to concede that the statement that lions eat meat is completely true. We have observed this phenomenon first-hand on the plains of Africa and can verify that it is in fact, a fact. It is also totally irrelevant to the argument at hand. Marshaling the claim that lions and other non-human animals eat meat as a defense of meat-eating among human beings is a classic example of the Naturalistic Fallacy, which is the erroneous assumption that anything that occurs in nature is therefore morally justifiable. This is of course ludicrous. Rape, murder, infanticide, necrophilia, and myriad other atrocities from which all well-adjusted people quite naturally recoil occur all the time in the wild, but no one is going to argue that their mere occurrence constitutes a moral or ethical justification for them. Nor do civilized people take their cues from the natural world by greeting one another –as lions are known to do– with a robust olfactory assessment of one another's hind-quarters. In polite society, such lion-like behavior simply will not do.

In biological terms, a lion is a predator and committed carnivore who has no choice but to hunt prey animals and eat them. If he does not, he will quickly perish. This is simply not the case with Homo sapiens, who are, anatomically speaking, frugivores. If you are reading this, you are not a lion and what applies to the lion with regard to sustenance does not apply to you. And what applies to you in terms of morality does not apply to the lion. Human beings are moral agents, whereas lions (so far as we can tell) are not and that, more than anything else, is the difference that makes the difference.

Your argument is invalid.