Which is worse? "A" lying about "B" in the public forum, or "B" publicly publishing private messages to clear their name of "A's" lies?

This a terrible situation to be in. While someone might feel the need to post a story, question or comment when they are hurting - no one should ever name names or hatefully out another. There is no good answer to your dilemma. So do the best you can, don't do anything to cause yourself to feel bad later on, and remember...the people who know you, already know what kind of decent person you are.