Understanding another’s dysfunction or mental problems helps one cope with injustice if you encounter that situation. But it doesn’t mean you need to embrace it or live with it or forgive it. Often in these situations it’s a matter of save yourself first if you happen to be the victim. If forgiveness helps you heal, do it.
As to the above quote–I’m not sure of your point. I think the point by Billy Graham was that nobody’s perfect and nobody can judge someone else. Leave the judgement to God. All you can do is live your life to your best ability and try to be a good example to others.