'sticking a pin through a butterfly'

When romances do really teach anything, or produce any effective operation, it is usually through a far more subtile process than the ostensible one. The Author has considered it hardly worth his while, therefore, relentlessly to impale the story with a moral, as with an iron rod—or rather, as by sticking a pin through a butterfly—thus at once depriving it of life, and causing it to stiffen in an ungainly and unnatural attitude.

—Nathaniel Hawthorne, preface to The House of the Seven Gables (1851)