Grandma Peace Brigade

Over the weekend, I was on the subway and saw this old lady with a pin stating "Grandma Peace Brigade".

I was wondering what it means.  Then I thought about one incident that I took Tres and baby out for lunch. The weather was nice and I tied Tres outside of a local falafel place called Pita Grill (where is my Sido on the east side?).  I sat right next to the window so that I can see Tres clearly.  There were many people stopped by and pet Tres.  Then, this older lady who saw Tres sitting outside and she got so mad.  She told me that this was wrong to tie the dog outside of the store and she was going to report me to the animal cruelty agency.  Was that woman from the Grandma Peace Brigade?