I've been on the receiving end of this behaviour also.
Sitting in a sport and social club, with my two dds aged 1 and 2, and the people we were sitting with had a 2 ish year old child who announced that he needed a poo. They whipped out a potty and sat him upon it Right in the middle of the sports and social club.
I was astounded. The club steward was a friend of mine, so I busybodily went to report this to her.
The club steward (who, by the way, had no children) sallied forth and asked them not to let their two year old child shit in the lounge bar.
"What's the harm? We brought our own potty!"
That was years ago, and we still see them out and about.
But to this day, I can't understand how they could ever think that was OK.
By the same token, they cannot understand what all the fuss was about. What irked me most about that was that my two year old had substantial and severe LD, but I would never have used that as an excuse to let her shit in public. She's now 30+ and is doubly incontinent and wears pads 24/7
However, I can quite confidently say that nobody, in a social setting, would ever know that. What annoys me greatly is that 'normal' kids are allowed, by some blasé parents, to empty their guts in public.
I spent most of the time when I was out socially to make absolutely sure that DIDN'T happen.
Normal child shits in a pot in public = what's the problem?
SN child shits nappy in public = Embarrassment all round.
Soz. Rant over