A shared memory can belong to several people without being equally comfortable for all of them to publish.

A memory several people were present for belongs to all of them, but publishing it is a different act from remembering it. What reads as a fond story to you may be the worst month of somebody else’s life, or a version of themselves they have worked hard to leave behind. Having been there does not confer sole rights to broadcast it. The disagreement is usually about exposure rather than accuracy.

Ask the others before you post the photograph or tell the story publicly. Take a no without requiring a reason for it, and remove things promptly if you are asked later.