On his deathbed, Mr. Hooper points out the irony that "men avoided [him], and women show[ed] no pity, and children screamed and fled" from him because of the black veil he wears. It is ironic and, to him, absurd that people would treat him differently, would be frightened of him, all because he wears this piece of cloth over his face when, really, the thing that makes that piece of cloth so terrible is what it stands for; it is not terrible in and of itself. He says,

"Tremble also at each other! [....] When the friend shows his inmost heart to his friend; the lover to his best beloved; when man does not vainly shrink from the eye of his Creator, loathsomely treasuring up the secret of his sin; then deem me a monster, for the symbol beneath which I have lived, and die! I look around me, and, lo! on every visage a Black Veil!"

He identifies the symbolism of the black veil: it is a material representation of an intangible truth about humanity. We all endeavor to hide our secret sinful natures from our fellows, holding up a figurative veil between ourselves and everyone else. We even try, without success, to hide our sins from God in this way. We pretend, for all the world, that we are sinless creatures. Mr. Hooper, unwilling to continue this charade, began to wear the veil as a symbol of this attempt to hide our secret sins, an attempt that all humans make, and -- rather than realize what it meant and fear each other because of those natures and sins that they hide -- people instead chose to fear Mr. Hooper himself simply because of the veil.