Animals are resources; part of what sustains us. And for many of the 6+ billion people on this earth it is a luxury they cannot afford and, in fact, need more of. I assume you would not attempt to sustain your objection to killing in parts of Africa or Asia where the population is malnourished and in desperate need of protein? Or does necessity suddenly make animal slaughter acceptable?

There are a plethora of good reasons for the fortunate living in advanced societies to abandon meat, not the least of which is the environment. However, objecting to killing animals on moral grounds makes each act of animal slaughter evil. Thus, through the course of countless millennium of human history each animal slaughter was at best a necessary evil. I cannot adopt a worldview in which our ancestors were basically forced to commonly commit such "immoral" acts simply to survive, even if such a view gives me the self-indulgent satisfaction that, in a world full of suffering, that of the animals does not go unnoticed.