Well, to throw a whole new wrench into this, a lot of scientists believe that we evolved away from the other primates and developed a larger brain, and even language because we learned to hunt. Hunting, especially for a creature without fang or claw, required tools. We needed to develop training methods for our children and others, and strategies to hunt. We needed flexibility and creativity because animals changed, and circumstances changed - we had to learn to think on our feet. And some think that language started as a way to communicate during the hunt. A few simple warnings spoken because hand signals and other ways of communication would not be noticed when all eyes are concentrating on the task at hand.
Now, keep in mind that during most of our past, meat has been a luxury. It's only been in the past 50 or so years that average people can afford meat on a daily basis. Given this, I would say that the problem the world is facing right now is not that we eat meat, but that we eat too much meat and not enough other stuff. I do eat meat, but I limit all my animal products (including dairy and eggs) to once a day at most - often I don't eat any at all. I am a firm believer in all things in moderation.
However, if you come to my house and I know you're vegan, I'm going to cook vegan for you as I also believe that people have a right to believe what they want to believe. If you believe that killing animals is immoral, then that is your choice and I'm going to respect it.