I administer a few groups on FB. I have deleted posts. Posts that were relevant to the group itself but that were, IMO, detrimental in general.
Here's a broad example. I am on the board of a civic association. We do all sorts of stuff for the community at large. We do demographic specific stuff (aimed at kids, aimed at seniors, etc) and some stuff that is just for everyone in the community. Recently we offered free tickets to a major league baseball game, to anyone who asked for them, on first come first served basis. This was promoted on our FB page.
One member - not a board member, just an average joe community member - posted suggesting we donate these tickets to low income youth. I deleted it.
Its not that it was such a terrible suggestion, in fact I'm sure it was well intended. And it was relevant to our organization as a whole - we do do things for low income folks, and a lot for youths in general. But the fact is, this event, the board had decided was for everyone in the community. So I deleted it because I didn't want to have other people feel put off from requesting tickets, or start debate over whether we do enough for youths affected by low income households, etc.
So is it possible that while the overall topic was relevant the direction a particular thread was headed was inappropriate? In my case, had this same man posed a totally separate, stand alone question asking what events and plans we had for low income youths, I would have gladly answered and had a thread running about that. But he didn't, he posted it on the thread about an event aimed towards all, which I found inappropriate.