You know, I bet nearly every poster here has been confronted about something they posted. Often times a message is misinterpreted because we can't see the body language or hear the tone of voice. It has happened to me and I have seen it happen to others.
Deciding whether a message is not on topic enough has to be a tough determination. Give yourself some time to figure out how to react to the questionable posts.
One of the posted ideas I liked was to simply move questionable off-topic messages to the OFF TOPIC FORUM. That way the message is still available for all to read, and the rest of us will get the idea of which board our message is most appropriate.
Hopefully, you will reconsider and remain a forum leader.