What would you have done?

So today Daddy insisted we visit West Edmonton Mall...on a SATURDAY!!! This is not a regular occurance in our household. Honestly I avoid that place like the plague on weekends!! It is way to crowded and really, one of the few perks of shift work is avoiding crowded places on weekends. As I was waiting for the elevator a mom came out of little store yelling. "I CAN'T SHOP WITH HER!!!" indicating her three or four year old who was crying. Whoever was waiting outside calmly stated "Then leave her here, I'll watch her." Instead the mother grab the girls upper arm and yelled "For F**CKS SAKE" and marched her off! She yelled it loudly enough to silence everyone around us, and again the mall was packed! I was disgusted so I turned to tell her exactly what I thought. I mean someone has to stand up for this child. Unfortunately I had Everett in the stroller and was surrounded and couldn't get to her. There we at least 60 people who witnessed this and no one said anything , although I sure tried. Is this group think? Am I wrong? Should I have fallowed them? I feel that no child, especially young child deserves to be sworn at. I also know the risks of dislocating a shoulder in young children and although usually unintentional it does happen frequently. If a mother is going to behave like this in public what happens at home? I completely understand that shopping with a little one can be so frustrating, and I know that the mall was packed making it even more stressful, but does that make this behavior okay? And do I have a right to judge, speak up or interfere?