The original question had to be edited. I think that the issue of moral blindness is probably one of the most important issues in the story. Essentially, moral blindness is everywhere. The story is filled with characters who lack a moral vision. Nearly everything that is done is meant to satisfy some type of personal goal or self- indulgent wish, and little is present that keeps an eye on the social maintenance of a moral or ethical order. It is not that these are bad people, as much as they are morally myopic. It is here in which blindness happens.
Certainly, Matt and Ruth suffer from moral blindness. They are blind enough to believe that the pain over the loss of their own son can be eliminated through Richard's death. Their vengeance prevents them from seeing an full range moral reflection. Willis suffers from moral blindness in his willing participation in premeditated murder. Frank suffers from moral blindness as he does not fully contemplate the consequences of his actions in his involvement with Mary Ann, who in turn suffers from a limited vision of her own interactions both within and outside the realm of marriage. Richard's moral blindness is evident in how he sees Frank as an obstacle to his own potential plans for happiness. In the end, there seems to be little else but moral blindness. The "killings" that result from this become evidence of this barren moral vision.