A good dog never barks at fault.
More French Proverbs:
To a rogue a rogue and a half.French
One must talk soothingly to the dog until one has passed him.
French
It is just that the priest should live by the altar.
French
The bird ought not to soil its own nest.
French
Economy is the wealth of the poor and the wisdom of the rich.
French
A fault denied is twice committed.
French