The fact that y'all would offer to police poor admin behavior is better than the norm in the first place. I haven't heard of it being enforced, but you'd know much better than I how well and if you do.
You ain't the US government, so you have no obligation to not suppress speech. I'm just making the point that the bare minimum social cost for poor behavior is for people to know about it. When that minimum cost is removed or suppressed, it usually ends poorly. Your reasons for the rule make sense, but some of the people who were badmouthing the servers had good reasons to do so too. Sometimes harm to reputation is earned directly by poor behavior.