This is untrue. For example, Copper Sulfate is a moderately toxic substance used in organic farming and is highly corrosive. It is approximately 5 to 10 times more toxic than Glyphosate (LD50 of ~300 to 790 mg/kg for Copper Sulfate vs. >4,320 mg/kg for Glyphosate.)
https://npic.orst.edu/factsheets/archive/cuso4tech.html https://npic.orst.edu/factsheets/archive/glyphotech.html