I think you should separate religion from researches and official recommendations like RDA...
For me raw foodism(as an example of 6-7% like you say protein diet) is more a religion - it's up to you to believe or not...
If you want to know what science have to say, you can read this
http://www.veganhealth.org/articles/protein----
You can survive at low protein diet... cause it's not like if you have deficiency you'll die next week...
But you will build lower mass if any, compared to well planned vegan diet...
You can also find it takes longer to recover after intense workout...
I know some people , sit on low protein diet, cause they don't want to build additional muscule mass...
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Very often when promoting veganism you will tell to people that, protein deficiency it’s a myth… but yes maybe it’s rare cause there is no visible consicuances of not severe deficiency…
But I think 50% of vegans are deficiency at essential amino-acids…
Just look at the table at the site I gave ya, and you wil understand why I think so