>His point was they are/were using chemicals regardless of if they understood the chemistry at a low level or not.

Even if that was his point, it is still completely wrong.

>It is impossible to produce food without chemicals.

If you live in the northern hemisphere, it is only June. Go plant a handful of pumpkin and watermelon seeds in a patch of fertile earth. Add no "chemicals" of any kind - man made or otherwise. Return in 4 months and you will very likely see food that has been grown with absolutely no chemicals at all.