I like what H4U said. If it is about foisting pain on someone else, then it doesn't make sense. If it is about doing the right thing, protecting the innocent, or righting wrongs, then, done delicately and compassionately, "telling people" can be helpful.
In general, it's good to be completely honest, but sometimes complete honesty, especially about the past, can be unnecessarily hurtful. Honesty about the past does not always win, in my view. It has to be balanced with compassion. "Even if it is true, will what I want to say, hurt people if I say it?"
