First, the sample size of those observed are small compared to the overall size of the Civcraft server. Sure, if you only spend most or all your time on the Mumble server, then you probably care little or not at all for what goes on in-game. However, the Civcraft community is bigger than the Mumble server.
Second, the loudness of the liked or disliked people affects one's perception. By loudness, I mean how often someone talks. For instance, a hundred people can join the Mumble server and just listen; their presence is moot as to whether or not one considers the server to be diluted by immature individuals. That is, if you never hear someone communicate, then they are irrelevant, superfluous, to the community. However, there are many players who never join the Mumble server.
What matters to these people who are concerned with the increase of morons on Civcraft is that they perceive a social change. Unless they are taking care to watch the in-game community as well as the Mumble and subreddit, then they have a limited view of what is going on Civcraft.
Afterall, the point of Civcraft is to play Minecraft. I think it is these concerned individuals who have lost sight of the purpose of Civcraft. Yes, Civcraft involves community, but it is about the experiment of Civcraft first, with the social and economic layers as the stuff that makes the experiment human and challenging.