One sees not but he had best let bad take care of itself, and have to do only with what is beyond suspicion. If you light on the least vestige of truth, and it is the weight of the whole body still which stamps the faintest trace, an eternity will not suffice to extol it, while no evil is so huge, but you grudge to bestow on it a moment of hate.
 Henry David Thoreau, A Week on the Concord and Merrimack Rivers (1849). copy citation

Context

“stand but just outside the faults they condemn, and so are concerned rather about the monster which they have escaped, than the fair prospect before them. Let them live on an age, and they will have travelled out of his shadow and reach, and found other objects to ponder. As long as there is satire, the poet is, as it were, particeps criminis. One sees not but he had best let bad take care of itself, and have to do only with what is beyond suspicion. If you light on the least vestige of truth, and it is the weight of the whole body still which stamps the faintest trace, an eternity will not suffice to extol it, while no evil is so huge, but you grudge to bestow on it a moment of hate. Truth never turns to rebuke falsehood; her own straightforwardness is the severest correction. Horace would not have written satire so well if he had not been inspired by it, as by a passion, and fondly cherished his vein.” source