Thinking about it right now after several shots, forgiveness seems important to modern fucking love science enlightenment logic. We are exposed to so much foulness yet that foulness is so "far away" that it doesn't affect you directly so you can sit back and think "Was this really that bad; is this tolerable; is the person who did something maybe intolerable still useful"
Forgiveness is too strong a way to put it, but there is a pervasive sense that despite some mortal sin, the person who did it is still a person and is still at least potentially useful for not-evil things. They might have even done the evil thing for a "good" reason to them. Not like "he fucked that child because the child was sexy" but "that man's sexual tastes are fucked up because he got fucked as a child (and we can let him know that that wasn't ok and it wasn't his fault so he doesn't continue that cycle of abuse)". It's why we have rehabilitative justice
But to maybe PL, I don't think anyone can be truly forgiven, and forgiveness is not useful. But I don't think true evil is real either. Whoever you are and whatever you've done will persist forever; ethics and justice aside, people have memories, and your own past experience will influence your future operations. People are as they are and can only be added to, not completely rewritten. "Forgiveness" is admitting that we're all in a complex situation and hoping that the person who did a no-no learned from the experience and had a good reason for doing whatever they did in the first place. To be forgiven is only to get a second chance; to forgive is to admit you didn't have complete information when you got mad.