Many people are of the opinion that if one is a Christian one is not obligated to be a vegetarian, nor is it even supererogatory to be a vegetarian.This argument can be challenged in several ways, here I will offer one quick argument to the contrary:
1. In the perfect state of nature humans are vegetarian
This is shown by the vegetarian diet in the Garden of Eden before the fall, and as well as "prophetic" verses concerning the lion and the lamb getting along nicely. In other words before the fall, and in "heaven" humans were and will be vegetarian. I think this is fundamentally correct, and see no problems with this premise.
2. In the perfect state of nature humans were closest to God (had a better relationship w/ God, etc.)
This premise can be modified in multiple ways, what is important is that in the perfect state of nature the Christian can better fulfill their calling and purpose as a Christian. In other words it would have been preferable for humans, not to fall and to remain in the perfect state of nature.
3. As a Christian one ought to be close to God
This premise can also be modified in the same manner as 2.
4. Therefore, as a Christian one ought to emulate the perfect state of nature.
5. Hence, as a Christian one ought to be vegetarian.
I think this is a legitimate argument. I can think of a few objections, one is that in the Bible people frequently eat meat. For this objection to work it would have to be rephrased along the lines of, God condoned x as morally permissible therefore x is morally permissible (as opposed to the clearly fallacious: person x does y in the Bible therefore y is morally permissible.) At no point that I am aware of does the Christian God say that eating meat is morally obligatory, only that it is permissible. Later on the apostle Paul seems to contradict himself with Romans 14:21:
"It is better not to eat meat or drink wine or to do anything else that will cause your brother to fall."
and Romans 14:02:
"One man’s faith allows him to eat everything, but another man, whose faith is weak, eats only vegetables."
These two verses can be interpreted in multiple different ways and have been used to argue both for Christian vegetarianism and against it. I am not sure that any one make any ground on this argument (here is a short rebuke of Rom 14:02), at any rate lets assume that eating meat is neither obligatory nor forbidden and likewise for vegetarianism. How does this affect the argument? It may mean that it is not obligatory for a Christian to be vegetarian. I am not sure if I follow this objection, but lets consider it valid. All this establishes is that the it is permissible for a Christian to be a meat eater, but it would be better if they practiced vegetarianism. In other words it is supererogatory that Christians be vegetarianism if this objection is correct. In other words if eating meat is permissible, then being vegetarian is not obligatory, but it still may be better.
I think if the advocate for Christian vegetarianism is to overcome this objection they may do this by making a crucial distinction. God (and Paul and whoever else) say that eating meat is permissible after the fall, this is not to say that it is desirable. In other words humans ought not have fallen, this being the case things that are permissible after the fall, may not really be ultimately permissible. Thus it is ultimately the case that Christians ought to be vegetarian.
I am not yet convinced if this argument works, I think I will try it and see what people say in response. It may ultimately come down to theological interpretation and whatnot.