I think we should put this travesty behind us as fast as possible, but there is also the concern of changing convictions of what was then a legitimate crime. I read from a legal expert who said this might set a legal precedent of others looking for changes in laws that will free them now. For instance, if a person is found guilty of a crime, but public and political outrage caused a change of law, that person may then be freed with this law, even though the conviction is legitimate. It might also be used as precedent for the other way apparentely (although that sounded... weak) of people getting convicted for crimes that were not illegal at the time of doing it.
That said: despite the legal consequences, I'm leaning to your position. After all: we're not Uganda or India and should distance ourselves as much as possible.