In the case of war stories, I would use the flip chart to record what they’re saying. Often, people just want to be heard. And once you capture what they consider the “root causes” of the lack of success, then you can ask the team to brainstorm what you could do to avoid that kind of failure going forward. Treat it as something to learn from in the same way that we use the FMEA (Failure Modes and Effects Analysis) to uncover potential failures and then work on mistake proofing methods to avoid those failures associated with change. Use the war stories as just more data.