I'd just like to point out that there are more than two reasons that a person might choose to not eat meat, other than for moral reasons and health reasons, as you state. I, personally, don't eat meat, because I, personally, don't want to put dead flesh in my mouth, chew on it, and swallow it. But I have no problem with people who do want to do those things, and have cooked meat for every significant other I've had, and currently cook meat for my son when he's with me (though I feed him meatless meals as much as I can, because he gets meat in his school lunches and I'm cheap and lazy).
I don't want to be personally involved with killing an animal, nor do I want to see it die, but if I were involved with someone who hunts, I would probably go on the hunting trip (just not out in the woods to shoot), and would LOVE the chance to help field dress a deer. (And would want to know that it's going to become food, not a trophy.)
I do think our country could do a much better job of raising meat animals, slaughtering them, and butchering them, but am not going to try to stop those who choose to eat anything from their pet to the pre-packaged stuff at the grocery store. People at work are always apologizing for eating meat in front of me when they remember I'm vegetarian, but I totally don't mind, as long as they don't shove it down my throat (literally).
I also don't see the correlation between eating meat and using an animal for other purposes. In some ways one is worse, in others it's the other way around. For example, a cow raised in a pasture with pasture buddies, then led behind the barn and shot where it is standing such that it doesn't have a clue what's about to happen, or what happened, just that one moment it's happy and the next it doesn't exist? That's probably a better life than that of a plow horse that is worked HARD every day with very little comfort or care. A pampered horse, on the other hand, has a much better life than a veal calf or feedlot steer. It's all a matter of perspective and the actual experiences of the individual creatures. My cats are pampered and spoiled and have had some veterinary intervention. My one cat, especially, who was born under a dumpster, has had a much better life than she would have, I'm sure.
Your example of wild horses not running into barns isn't very appropriate, either. Wild horses prefer what they KNOW. Not just horses, but any wild animal only knows being wild, and has instincts that tell it that civilization (humans, man-made improvements to the land) are scary. Domesticated animals see humans as their source of food, comfort, and often companionship. Therefore wild animals will generally avoid humans, while domesticated animals will often choose humans over the "wild." Not to mention, animals aren't capable of seeing both sides, conceptualizing things they haven't experienced, and rationalizing it out. A wild horse, therefore, has no ability to "prefer" anything other than what its instincts tell it. If it COULD have higher thought capabilities, though, imagine how that would go. You could sit that horse down, explain domesticated life to it, and that while it would be cooped up in a pen, and sometimes have the indignities of being tacked up and ridden by humans, it would also be provided with excellent health care, guaranteed food, and some pleasurable activities it enjoys (some horses certainly seem to "enjoy" grooming and even being ridden in certain disciplines, and I bet the studs, at least, enjoy breeding
). The horse might mull it over and make a rational decision. Some horses might decide on the domestic life, and some might still prefer to take their chances in the wild. Who knows! (It's kinda fun to think about though, isn't it?) But you can't say because a wild horse doesn't just run into a barn and throw a saddle on its own back and begin performing a piaffe, that horses in general would rather be wild than be ridden.
(ETA some clarification and grammar fixes)