I wonder if anyone could be considered sane after murdering so many people in cold blood. I mean, why is there even a discussion? Because he's not wearing a strait jacket and a napoleon hat but a suit?
I agree with "beef" on the preservation argument. It was what also allowed humanity to expand all over the globe. If you think about it, "omnivore" just means that you can eat anything, so when there was no meat, humans could still survive.