I get it, I really do. I struggle with what to tell my D5 about why we got divorced if she ever asks... "*We*" decided we couldn't be married anymore doesn't feel true to me. I totally hear what you are saying about wanting to pass on your values to your kids.
But I have a hunch they know where you stand. And I think you can be cordial to someone without teeing their friend.
I got an email from MWD today that discussed how forgiveness is a gift you give yourself. (I would add that it's a gift you give your kids, too.. to show them that we can have the capacity to forgive, even if we don't forget).
