Okay, so I spoke to some people who have been in the industry since before I was born.
It seems that, generally, wear your 'droppings' on an airfield, and only on an airfield. The rest of the time keep your ego, and 'droppings', in your shirt pocket.
Other times that it is generally accepted to wear them are when you need to do official business, that requires you to be identified as a pilot, e.g. filing flight plans, need to go for some official business at an aviation related organization...
or
when traveling, for example, from SA to let say Angola, where they can be quite difficult at customs. This shows the officials that you are crew, and it makes life MUCH easier when entering the country.
As for seeing people wear their droppings in shopping centres, or anywhere else for that matter....
All I can say is.... shame.... go and give the poor boys a huggy. Their moma's probably didn't.