You cannot really talk sense with someone who abides by the principal, "if you're losing, shout louder."

So turn away from them and talk to someone else. And hope the shouters either move on or come to their senses in time, both of which things happen. (As has often been said, sometimes the best way to get listened to is to speak or sing in a soft voice, and be saying or singing something worth listening to.)

In fact there's never been more than a handful of people who go over the top - and they aren't the real problem - it's much more the people who get drawn into responding in kind, until we learn better.

I was looking at kat's list, and I agree, I miss a lot of those people - but I don't think we have to assume it's the squabbling that has driven them away. There are all kinds of reasons people give up doing something, mostly because other things in their life take up the time and the energy.