ah, "let he who is without sin throw the first stone" an oldie but a goodie. in other words, only the infallible may criticize anyone/thing? that seems count

ah, "let he who is without sin throw the first stone" an oldie but a goodie. in other words, only the infallible may criticize anyone/thing? that seems counterproductive. If my hair is messed up and i tell a stranger that their hair is messed up, does that make me wrong? should they ignore what i said because /my/ hair is messed up?