Not exactly true. There were plenty of cultures pre-modern-agriculture who lived on little to no animal products whatsoever. There are even still places where you can do that, in the wild, right now.
There is a WIDE variety of "modern agricultural technology" like greenhouses, aquaponics, hugleculture, etc. that is perfectly harmless, but those don't involve messing with DNA itself. Working in tandem with the plants & environment is a whole different story from trying to play god.
Lost any credibility there, as protein deficiency is almost impossible unless you aren't getting enough calories to survive anyway.
You did, and that is the proper term. My point though, is that any time someone references "not enough protein", it's clear there is some level of misunderstanding nutrition and nurtritional sources. (not necessarily you, as I assume you're giving an example of something they said in the documentary)
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: