Make room for the other version
Ask what the other person understood before assuming that you are arguing about the same facts. For a message about how to keep medical information private from family, use this factual base: identify the visit, topic, money, photo, event, care task, or comment that needs a limit.
Correct the record precisely
Correct only what you can support, acknowledge any real impact, and propose a practical way to prevent repetition. State what is allowed, what is not, and how you will respond consistently. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Agree on a testable next step
Do not threaten access to children or elders as punishment, and do not debate the entire family history. Use safeguarding, legal, domestic abuse, or emergency support where safety, custody, or coercive control is involved. Do not recruit an audience, publish private evidence, or turn a misunderstanding into a campaign about character.