It's an interesting idea. Law, justice systems, were all created in order to adjudicate that level of animosity and prevent it passing on to future generations. Holding on to a grudge, not even out of a sense of justice, but purely out of hate, seems like a path towards poor mental health. But I'm lucky enough to not have any hate that strong -- those I've chosen not to forgive I've instead chosen to forget, which is a privilege relative to the level of wrongs done.