I agree we should find it in ourselves to forgive our parents/guardians for what they've done to us as children. They only did what they knew how to do; they're only repeating what they've learned. I don't believe holding grudges, carrying around that hate or hurt is healthy. I'm still coming to terms with all that I've experienced when I was a child. As for the person who said they would never forgive them, they are likely still hurt from the things they've experienced as a child and need time to heal fully.
Indeed, I agree with the "usually" part of this sentence. A lot is going on in the world right now. Sometimes people learn from their mistakes, but they don't care to put that knowledge into action, unfortunately.