Pardoning the bad is injuring the good.
More German Proverbs:
Tis easier to hurt than heal.German
He who is his own teacher, has a fool for his pupil.
German
He who invites storks must have frogs in the house.
German
Plants oft removed never thrive.
German
Stretch yourself according to your cover-lid.
German
The best friends are in one's purse.
German