The Greens are basically opposed to anyhting that makes life better for humankind. Cattle are a source of food for most people. For the Environuts, that is bad. If humans are well-fed, then they might be, Horrors!, healthy and multiply. Also, anyhting pursued by modern man is mucho evil in the eye of the Environuts.
Well I love beef but buffalo IS better. I was just thinking we could solve the pollution problem (shutting up the nutcakes), have better dinners and, as a bonus, we would have buffalo everywhere instead of cows. I figure that would be a bonus because it would be a nice tribute to the 'first Americans' and a retro way of paying homage to the uniqueness and abundance of this continent which we call home. Much lower cholesterol too.