What positive effect does the black veil have? Nathaniel Hawthorne's "The Minister's Black Veil"

As narrator of
","writes,

Among all its bad influences, the
black veil had the one desirable effect, of making its wearer a very efficient clergyman. By the
aid of his mysterious emblem--for there was no other apparent cause--he became a man of awful
power over souls that were in agony for sin.

Within the
Puritan community, people hoped that they were among the "elect"; however, since there
was no way of knowing with certainty, they tried to live as exemplary a life as they could. 
With this ideological condition of being sinless, those who did transgress kept their sins a
secret.

Now, when the Reverend Hooper dons the black veil, the congregation
begin to doubt his sinlessness and become uncomfortable around him for this reason and for the
probability that he may recognize sin in themselves.Thus, the veil becomes "the symbol of a
fearful secret between him and them."  But, the veil "enabled him to sympathize with
all dark affections."  The dying call for him as a brother before whom they can confess
their hidden transgressions; he is "ever summoned to their aid in mortal
anguish."

Ironically, the Puritan minister comes to be called Father
Hooper; for, much like the Catholic priest, he is summoned to hear one's confession before he
dies.