Joseph demonstrates his love and kindness for them, in the face of all they have done, and seeing that they still carry the guilt of their sin, by saying:
"Fear not: for am I in the place of God? But as for you, ye thought evil against me; but God meant it unto good, to bring to pass, as it is this day, to save much people alive. Now therefore fear ye not: I will nourish you, and your little ones." And he comforted them, and spake kindly unto them.
This is years after Joseph's family came to Egypt, and his brothers are still ridden with fear. Joseph has moved past his earlier trials and can even see a good that came of them.
Joseph's compassion is beautiful. I would probably have said something like, "Are you still on that old theme? Just stop bringing it up, okay? It's done with. Yes, you did wrong. Yes, you deserved justice and received mercy. Deal with it." But Joseph's brothers, instead of thanking the Lord that He dealt mercifully with them, are still looking around wondering when the knife will fall. They just can't be comforted. There is something missing from their view of life. I think it must be a close walk with the Lord. They are still trying to grasp their assurance of safety on their own, are still trying to save themselves rather than trusting the Lord.
Joseph's continuing demonstration of love for his brothers is a good example to follow. He is so patient with them as they keep bringing this up, perhaps understanding the nature of their torment. He even weeps over it every time it manifests itself in their actions. But Joseph was a very tenderhearted guy, I think. A little arrogant as a youngster, but what a good heart he had.