How does the notion of "the more private the character, the more sinister the intentions" come into play in The Scarlet Letter?

This quote
pertains most completely to Chillingworth. Chillingworth is a secretive individual who has evil
intentions.

Chillingworth getsto agree not to let anyone know he is her
husband when he returns to town. He doesn't want to be associated with the shame of her scarlet
letter. However, an added advantage to the secrecy is that it gives him power.

Chillingworth uses this power with sinister intent against . He realizes that
Dimmesdale is the father of . It is much easier for him to make Dimmesdale suffer because
Dimmesdale has no reason to suspect Chillingworth would have any reason to hate him.

Chillingworth, especially in his role as a doctor, is able to cosy up to Dimmesdale and
become close to him, in order to make his enemy's conscience writhe. The townspeople understand
that Chillingworth is evil and see him as being sent by Satan to test their good pastor, who
they have no doubt will prevail. Public opinion is that Dimmesdale is:

haunted either by Satan himself, or Satan's emissary, in the guise
of old .

Dimmesdale does suffer greatly from
Chillingworth, though eventually, at least for a brief moment, he does
prevail.