Well your english is quite good :-) "not enough protein" is one of the most common, though factually incorrect, arguments against veganism.

Absolutely, the soil (and microbiology in it) is just about the most important thing for the survival of humans, and every other living thing on the planet.

I would argue your last point a bit, it is quite easy (not simple, but with the knowledge, easy) to revitalize the soil.

Even in pure desert, we can create lush food forests: