Sergei and P&M raise some good points. Personally I'm not a vegan, but i enjoy vegan and vegetarian cuisine. Indeed one of the best meals I've had this year was vegan. I subscribe to the view that we're omnivores (not carnivores Cabbage). I know someone who ate a lot of meat but wouldn't eat anything green before the age of 20. Being scrawny, pasty faced and suffering bowel problems isn't the sole privilege of vegans!
One of biggest problems with western society is the increasing availability of cheap food. This has translated into larger and larger portion sizes over the years, well beyond what a human body requires for sustenance. In particular meat intake has rocketed. When i was a kid in the sixties a burger was two ounces. Then McD introduced the quarter pounder. Now any self-respecting gastro pub has 8oz burgers on the menu. Same with steaks. There's a compelling case for reducing meat production, both for health and environmental reasons