Earlier quoted context omitted.
I want a source for that outrageous claim that the most environmentally damaging human endeavor is growing vegetables. I suspect you being right would turn the world on its head.
How many extra plants would you have to grow and use as fertilizer on plants if you didn't have animal fertilizer? Or do you want to rely on non organic farming methods for your plant only ethics based utopia?
Manure is used because it is readily available due to current livestock production, not because it's the only way to fertilize soil.