I kill a lot of rats for work (I'm not an exterminator; I'm a scientist!). "A lot" is, of course, a relative term, but suffice it to say that I've killed hundreds of rats with my own hands. Every time I have to feel the flesh being cut, and the bone breaking. It doesn't make me want to vomit anymore, but it took quite a long time to get used to. I think civilized people should have an aversion to killing. I also think that doing it at a distance (such as sticking a needle in an arm then pressing a button; or, as in your example, buying meat off a grocery store shelf) completely removes the gut-wrenching side of killing, which is really where it's humanity lay. It's east to pretend that the delicious ribeye on your plate has nothing whatever to do with a bolt to the brain of a once living steer. I'm guilty of that all the time. We are certainly willfully unconscious of it as a society. The way we kill prisoners is emblematic of a huge problem.