How do you deal with an ex who won't let the past die?

I'm talking about constantly badmouthing you to people over stufff that has happened years ago.How do you deal with an ex who won't let the past die?
When people tell you what they say, simply say, ';That is true but I'm glad I've grown since then and sorry they haven't';.How do you deal with an ex who won't let the past die?
You do not react to it. If you give attention this person actions they will continue to do those things. Do not let them have any credence in your life.