But just to comment on your first point, we would never let an animal suffer like that when we grew up. A quick shot to the temple to switch it off immediately, and then cut and hang the meat to bleed out worked just as well for us.
Don't get me wrong, we were always taught to minimise any suffering and to give our livestock the best/healthiest/least stressful lives possible, and to treat them with dignity when you needed them for food.
Note that in my story I did eat the meat - I may have understated how delicious it tasted. Freshly butchered pork made this way is unlike anything I've had in North America. Is killing for sustenance more moral than killing for sport, or for taste?
I don't pass judgement on people who hunt or slaughter animals this way, but I don't buy the idea that killing animals is simply a part of life and above moral consideration - or for that matter GP's argument, that it's perfectly moral to kill animals for food because it's as nature intended.
Anyways, I dislike the utilitarian/primitist argument because you can justify any number of cruelties with an appeal to nature. Cats play with their food all the time so why can't we torture animals for fun?
Humans should ponder the morality of killing animals because we have the will and ability to do so.