>You’ve gone out on a limb, so please substantiate your case.

I already did!

Original atmosphere and soil on this planet were toxic. (Conjectured or established) The microbes and plants for the most part reduced the toxicity to what we have today which sustains life as such. So they also balanced the CO2 and other gases.

So it is very hard for me to believe that these same plants and microbes could increase CO2 to dangerous levels for life.

It is also hard for me to digest how one could infer anything on these matters without paying attention the genetics of plants and microbes, hence my crackpot comment.