• why do both of them put out an empty hand?

Father and son both put out an empty hand because they seek to reach out to each other devoid of previous baggage. They come to each other without their own preconceived notions or conditions, they have chosen to forgive and forget. They have nothing common between each other anymore, nothing that can be shared. So they must start afresh from that state and possibly discover a common ground which can accommodate their divergent views of looking at life.