I am asked: “does Buddhism necessitate vegetarianism?”
Considering that Siddhartha wasn’t a vegetarian, I’d say “no”. On the other hand, there are lots of people who disagree. I think Stephen Mitchell wrote an extensive apologia for vegetarianism, although I can’t find a reference to it. (It may have been back in the old East-West Journal.) Here’s what I have heard.
The historical tradition is that one of the parts of Right Action is not to allow something to be killed specifically for your food. At the time Siddhartha was alive, a Buddhist monk was supposed to live on food freely given by others: this act of freely giving is called dana, and later on in the Theravada traditions, giving food was a way for a lay person to accumulate merit. As such, it was forbidden to pick and choose — if someone gave you brussels sprouts and beets, you ate brussels sprouts and beets. On the other hand, if someone gave you a leftover roast cow, you ate roast cow. And in fact the tradition is that Siddhartha died because he ate spoiled pork he got in his begging bowl. Being the World Honored One, of course, he knew it was spoiled, but he none the less wouldn’t refuse it. (And see peripheral Buddhist story below.) But in any case, this was effectively leftovers, not something killed just for him.
As time went on, different people had different ideas, and of course situations changed. In modern times, a Buddhist would generally not hunt unless it were the only possible way to survive or to keep others alive. (See discussion of the difference between what following the Precepts and “sin” means in this context below.) But is meat you get from a grocery store meat that was killed specifically for you?
My own opinion is that the Buddhist tradition also tells us that all life, even grass and such, is “sentient” life; it’s got as much “divine spark” as we do. Since we can’t avoid eating living things of some sort, then you should attempt to make sure that what you eat doesn’t suffer unduly — I won’t eat “live sashimi” in Japan — and you should give respect to what you do eat.
There’s another point here. The Eight Fold Path isn’t a list of Commandments. You don’t follow the Precepts because it’s sinful not to, you follow them for the same reason you follow a weights program if you’re a body-builder: because it’s been proven to be the most effective way to achieve a goal. The goal is to save all sentient beings from suffering by realizing the Real Nature of Things, and the Eight is simply an effective program. So, failing to perform one of the steps is more like breaking training; not sinful, just not efficient.
Peripheral Buddhist Story: when Siddhartha was in his 80’s he ate the spoiled meat, and was dying. he gathered his disciples around him, told each of them his last advice, told them to continue their practice, and, according to tradition, the last thing he said to them was “Attend to your own Enlightenment.”
It is, however, the secret tradition of my lineage that he actually said “Attend to your own Enlightenment … and watch out for the moo shu pork. That’ll kill ya.”