Forgiveness is about self-preservation more than anything else. It likely is a big reason why religion has the draw for many that it does, as religion usually builds this concept into its dogma. All part and parcel with a predefined moral code, so many look for in religious systems. It works great until it doesn't.
There is a difference between "forgiveness", and accepting things and moving on. The latter requires a level of self-actualization that most people do not have, so forgiveness comforts them.
I prefer to accept the damage and move on.
Oh, and society has no use for people like Dylann Roof.
d4g