Question: A person posts on a Facebook open forum page he manages about witnessing a fire and how he tried to help. Then stated how the fire department was slow to arrive at the scene. He said he didn't want to be quoted during private messaging, then posts it for everyone to see. Can I use this in my story, saying this is what was posted on Facebook?
Answer: Legally, yes printing truthful, accurate information in a public place will not lead to any liability. Particularly if it was posted on an “open forum” (presumably a Facebook page viewable by the general public, not just those invited to participate or closed and available only to friends).
Ethically, that's the reporter's call. If somebody says “please don¹t use this” and you do the opposite, there should be compelling reasons. This would certainly need more investigation on your part – this person said that the fire department was slow to arrive, but what was his expertise in judging response times?
Certainly it needs a comment from the fire department. And perhaps some investigation on fire department response times.