I don't know quite what it is that encourages tribalism, but it is astonishingly common, and I think it's probably largely informed by some sort of fear, and starts to dissolve the more people let themselves mix. Banjo jokes stop being quite so funny when you join a band, and although (if you visit some sites) you find that melodeon or diatonic players seem to regard themselves as a having attained a higher spiritual state removed from such children of the mud as we, those I meet down the pub seem to be perfectly tolerant. Of course, when I'm being a flautist, you should hear me on the subject of over-powered rhythm sections. I have even laid my head on the shoulder of a fiddler. Got the bow up my nose, but it was worth it.
I had an interesting experience lately when a number of box players were gathered together, and marked hostility was evinced by some people to playing anything on the left other than oompah base. I'm not sure the word 'decadent' wasn't applied to one particularly squidgy combination. My reaction was considerably modified when I discovered that the principal objectors were actually quite terrified of their playing being heard by anyone else, and had probably joined the group to conquer that fear and were hugely stressed, and felt they were being patronised, ridiculed and deliberately embarrassed.
Where demographic is really really helpful, and the scientific collection of it is invaluable, is where you are trying to get numbers of people to co-operate on anything, and you are going to be in terrible trouble if you don't understand everyone's background ,and what they want and what is likely to scare or make difficulty for them.
I'm just so glad I don't teach classes. The people that do are angels.