I was just arguing with a friend of mine about the ethics of killing, and it was an interesting discussion, so I thought I'd bring it here. I haven't asked my friend and thus don't have permission to quote them, but I can reveal my own ideas.
I am a mostly-vegetarian, not a vegetarian-through-conviction, although I see the suffering of many of the animals we raise for consumption and do not think it is a good thing. I choose to eat meat only occasionally because I simply think to eat meat only occasionally. I might go a few weeks without buying meat or meat-based products - there is plenty of protein in the legumes I love to eat, and plenty of vitamin B-12 in the mushrooms I love to eat, so there is really nothing meat supplies that is necessary to health that I don't routinely get from the rest of my diet, anyway.
When I eat meat I generally eat meat that has come from a butcher or supermarket. Someone else has killed the animal. Someone else has gutted it, and removed all the stinky-bits. Someone else has skinned it, and sold the leather. The stinky-bits, the shed blood, and structures like feet and heads have usually been sold off to fertiliser producers, making most of the so-called vegan products people buy not animal-free at all.
However. Much though I dislike fishing, I have had a partner who enjoyed it, and I killed fish that I later ate. I also once shot an emu with extensive truck-related injuries, which I then dismembered and ate later - emu meat is redder than beef, richer in iron, protein and B-12, and lower in fat, making it far healthier, as well as far less damaging to the Australian environemnt than any lifestock animal. After all, it is designed to be here, they aren't. Also, because the animal died suddenly rather than being carted around the country in terrifying trucks for many hours then chased down a race to its death, its flesh's flavour hadn't been tainted with terror-hormones.
If you are going to eat meat at all, it is much more ethical to kill - or be prepared to kill - your food yourself, than to pay someone else to do it for you so that you don't have to face the realities of the sacrifice that another living creature makes for your meal, so that you can pretend you had nothing to do with its death, and so that everything can be "nice" and you can lie to yourself about not being a killer. If you are not prepared to kill, don't pay someone to kill on your behalf, soullessly.
I have a friend who doesn't believe in killing. Mutual friends have told me that since their conversion to Buddhism, a conversion that is perfectly fine to me, they now spent a lot of time and effort chasing mosquitoes out of the house instead of slapping them against walls, because "mosquitoes have souls too". Do they refuse to take antibiotics, or herbs, or even refuse to get better and fight off infection through their unaided immune system, because microbes have souls, too? Do they examine the ground carefully instead of just walking, to make sure that every step doesn't take the life if an ant? I have seen them walk, and no, they don't look down and clear every foot-sized piece of ground before they tread on it. So there's hypocracy straight away - why is a mosquito's soul and life-force more important than an ant's, when mosquitoes prey on us and are our natural enemies, and ants don't and aren't?
Then, this same person still eats meat. The same mutual friends have assured me that this is okay, because he doesn't kill the meat himself. All that tells me is that he doesn't have the honesty and integrity to look the animal in the eye and face the reality of the impact that he is having on the life of that animal. Without killing it, he doesn't have a chance to own the impact he is having on the life of that creature, to breathe a silent apology to it as he kills it, to make the killing as clean and painless as possible, to go into trance and guide its soul to the afterlife. Instead, he condemns it to terror in a cold and unfeeling abbatoir where nobody gives a damn about it.
Strangely, as an unenlightened non-Buddhist, I have a big problem with this!