So cows fart, big deal. If the vegans win and everyone gives up meat, then that means a hell of a lot more more crops will need to be planted and harvested.
That means one of three things. More people growing their own food on subsistence farms, or more machines burning fossil fuels to grow more crops on more land, or using more animals to do the work of machines in farming.
I don't see any net benefit to any of those options.