I was once a member of the VFW--the Veterans of Foreign Wars. I didn't have to esp0use any particular belief to join, i just had to provide reliable documentary evidence (my army discharge certificate) which showed that i am a veteran of a foreign war. I didn't have to believe anything in order to participate, and the organization was not promoting any beliefs.
The American Medical Association only requires that it's members be physicians, not that they have any particular belief set. With groups which are identifiable by family resemblance, your proposition is made to look even more ludicrous. I'm a man. That's true no matter what i believe. I am a native speaker of English--native speakers of English don't have to have any particular belief set to qualify as identifiable members of that group.
Your proposition that all groups are at the core about belief is nothing short of absurd, and even a modicum of thought shows this to be true. Really, i could go on for pages providing examples of groups which have nothing to do with belief.
The problem you will encounter here again and again is that people are not going to just accept your statements from authority, especially when they have no reason to assume that you possess any intellectual authority.
And stop being a whiner--no one is obliged to respect what you say, especially if you say silly things. If you want to offer your opinions, at least have the decency to tart the old whores up with a little make-up--you know, maybe offer a logical basis for your argument before you run off into the wild blue yonder with it.