Or put simply, who decides that a chicken has more of a right to live than a carrot? It's all empty-headed bullshit.
I've never been able to relate to the hostility shown by both sides of this issue. To me, it does seem to be a difficult, nuanced moral question. I especially don't understand the naturalistic argument, because in my view this isn't an "is" but an "ought" matter. I think a sensible starting line is whether or not the living thing you're eating has a nervous system, which quite clearly puts carrots and chickens in different camps.
I'm fairly undecided on this issue, but I can't help but shake the nagging feeling that I have some cognitive dissonance to work through. If you accept evolution (and I assume everyone here does) and you start with the premise that killing humans for food is morally wrong, then you're forced to evaluate the same question throughout the evolutionary tree (or bush, at is were). For those people that accept the premise and are settled on your side of the issue, presumably they have decided that the life of a chicken, or a pig, or a cow, or whatever has sufficiently low value to trade for convenience, nutrition, quality of life, health, etc. And these things will vary by person, admittedly -- in my case I suspect my eating meat is primarily a matter of convenience and quality of life. I doubt I need them to be healthy. But nor do I feel like I'm in a position to criticize those who are decided, except to discourage language like "wankoff jerkfest" used against those who hold differing opinions.
I'm reminded of Christopher Hitchens' position on abortion. He recognizes that it's a complex problem of spectrum. There can be no obvious line drawn through foetal development where you can say it's unambiguously morally ok to abort, so he's simply opposed to abortion at any stage for that reason (setting aside the mitigating factors like health risks, whether incest or rape was involved, etc.). To me, the moral question of meat-eating is similar non-obvious spectrum.