I think a lot of people have issues with their wrongs from the distant past. To the guilty one, this is a wrong they committed years and years ago, so to them it is distant history that they have since learned from and grown and changed. To the one just finding out, it is brand new information, so emotionally it might as well have just happened. Thing is, the guilty party has to empathise and understand that while it is ancient history to them, it is not for the one just finding out. As with so many such issues, being able to put yourself in the other person's shoes is so important.