I often seem to run into problems when I use the de facto label for this group. For example, when I say, "I've been hanging out with rationalists lately," I notice that many people immediately go on the defensive. They might ask why you need a group in order to be rational, or they might say that they don't believe that people are inherently rational. Of course, I made none of those claims, I simply indicated that I was hanging out with rationalists.
You might think that "rationalist" is simply a descriptive label, but it carries positive connotations -- and what people tend to hear is "I'm a superior thinker to you," or maybe "I'm a part of this group, which ascribes the label 'rationalist' to itself, to make ourselves seem higher status than we really are."
Why does this matter?
The community doesn't exist in a vacuum; how the community is viewed from the outside matters. As the community grows and as people gain awareness of it, branding becomes important. People talk to each other, and communities gain reputations. Even if you believe that we are a loose collection of individuals, as soon as you assign a name to yourself, that is sufficient to form a group identity.
The people we interact with tend to share similar interests. The population of New York may be in the millions, and yet I run into the same people at different functions without coordination.
The more negative perceptions associated with a group, the more rapidly evaporative cooling of groups will occur.
What to do?
It's far better to talk about good things that you've gained from being in the group. It's better to say what the group does, not what the group is.
But beyond that, it's about time the community picked a better label to use. I have one idea, but I'll hold off on proposing solutions.
People who join Mensa usually do it for signalling. People who criticize Mensa usually do it for signalling. Both groups enjoy the idea of being better than the other group. You could join Mensa and criticize it, for double signalling. I did. :D
I have met a few interesting people there, but the organization is mostly disappointing. It does not have a goal. Well, officially it does: the goal is to study intelligence and provide a stimulating environment for its members. But most members just meet and talk about whatever and also how intelligent they are and how the world does not reward their intelligence. I am afraid than any pseudoscience or conspiracy theory would be more welcome than rationality.
But if Mensa in your country is large enough, perhaps you could use it as a filter, find rational people inside Mensa, and start a local Bayesian conspiracy. Mensa can preselect intelligent people who search for something new. If Mensa will disappoint you, it will probably disappoint many new members too -- these people are already preselected for intelligence and searching for something new, just collect their contacts soon and send them to LW.