Why didn't I say anything?

I was at the grocery store walking down the aisle and a family was looking at something on the shelf. A little girl, maybe 2 or 3 was in the middle of the aisle. I had no problem, I would just have asked her to move. The mom grabs the little girl by the hair pulling her in the other direction and yells at her to move. I was immediatly sad and mad at the same time so what did I do...I walked away. =/ Why didn't I say anything?! Kids can't stand up for themselves, we have to do it for them. I just need more...what's the word without saying "balls" well, you get it. As I was checking out I started crying thinking about the little girl and how she wasn't at all effected by it so I assume it happens a lot...and I'm sure worse happens. Poor little baby girl, I wanted to scoop her up and give her a big hug. We won't say what I wanted to do to the mom.